19 (number)
| ||||
---|---|---|---|---|
nonadecimal | ||||
Factorization | prime | |||
Prime | 8th | |||
Divisors | 1, 19 | |||
Greek numeral | ΙΘ´ | |||
Roman numeral | XIX | |||
Binary | 100112 | |||
Ternary | 2013 | |||
Senary | 316 | |||
Octal | 238 | |||
Duodecimal | 1712 | |||
Hexadecimal | 1316 | |||
Hebrew numeral | י"ט | |||
Babylonian numeral | 𒌋𒐝 |
19 (nineteen) is the natural number following 18 and preceding 20. It is a prime number.
Mathematics
is the eighth
Number theory
19 is the maximum number of fourth powers needed to sum up to any natural number, and in the context of Waring's problem, 19 is the fourth value of g(k).[9]
The
19 is the sixth Heegner number.[12] 67 and 163, respectively the 19th and 38th prime numbers, are the two largest Heegner numbers, of nine total.
Prime properties
The sum of the squares of the first 19 primes is divisible by 19.[13]
19 is the first prime number that is not a
- 19 × 91 = Hardy-Ramanujan number or taxicab number, also a Harshad number in base-ten, as it's divisible by the sum of its digits, 19.[15][16]
- 1729 is also the nineteenth dodecagonal number.[17]
19, alongside
- Numbers of the form 10n9 equivalent to 10x + 9 with x = n + 1, where n is the number of zeros in the term, are prime for n = {0, 1, 2, 3, 8, 17, 21, 44, 48, 55, 68, 145, 201, 271, 2731, 4563}, and probably prime for n = {31811, 43187, 48109, 92691}.[19]
R19 is the second base-10
Figurate numbers and magic figures
19 is the third centered triangular number as well as the third centered hexagonal number.[21][22]
- The 19th triangular number is 190, equivalently the sum of the first 19 non-zero integers, that is also the sixth centered nonagonal number.[23][14]
- 19 is the first number in an infinite sequence of numbers in trailing zeroes in proportion to 9s present in the original number; i.e. 19900 is the 199th triangular number, and 1999000 is the 1999th.[24]
- Like 19, 199 and 1999 are also both prime, as are 199999 and 19999999. In fact, a number of the form 19n, where n is the number of nines that terminate in the number, is prime for:
The number of
- Distinguishably, the only nontrivial normal magic hexagon is composed of nineteen cells, where every diagonal of consecutive hexagons has sums equal to 38, or twice 19.[27]
- A hexaflexagon is a strip of nineteen alternating triangular faces that can flex into a regular hexagon, such that any two of six colorings on triangles can be oriented to align on opposite sides of the folded figure.[28]
- Nineteen is also the number of one-sided plane without turn-overs (and where holes are allowed).[29]
can be used to generate the first full, non-normal prime reciprocal magic square in decimal whose rows, columns and diagonals — in a 18 x 18 array — all generate a magic constant of 81 = 92.[30]
- The next prime number to generate a like-magic square in base-ten is , on the other hand, has a magic constant of 3439 = 19 × 181.[33]
In abstract algebra
The
In total, there are nineteen Coxeter groups of non-prismatic uniform honeycombs in the fourth dimension: five Coxeter honeycomb groups exist in Euclidean space, while the other fourteen Coxeter groups are compact and paracompact hyperbolic honeycomb groups.
- There are also specifically nineteen uniform honeycombs inside the Euclidean tesseractic honeycomb group in 4-space. In 5-space, there are nineteen uniform polytopes with simplex symmetry.
There are infinitely many finite-volume
- Vinberg polytopes of lowest rank n + 2 mirrors exist up through the seventeenth dimension, where there exists a unique figure with nineteen facets.[36] It is expressed with the simple Dynkin diagram, .
On the other hand, a cubic surface is the zero set in of a homogeneous
Finite simple groups
19 is the eighth consecutive
- Janko groups and are the two-smallest of six pariah groups that are not subquotients of , which contain 19 as the largest prime number that divides their orders.[39]
- holds (2,3,7) as standard generators (a,b,ab) that yield a semi-presentation where o(abab2) = 19, while holds as standard generators (2A, 3A, 19), where o([a, b]) = 9.[40][41]
- is the dimensionality of the minimal faithful complex representation of O'Nan group — the second-largest after of like-representation in and largest amongst the six pariahs[42] — whose value lies midway between primes (10939, 10949), the latter with a prime index of ,[43] which is the nineteenth tetrahedral number.[44]
- On the other hand, the Tits group , as the only non-strict
In the
Worth noting,
are added together, a sum of 19 is obtained.Science
- 19 is the atomic number of potassium.
- 19 years is very close to 235 lunations. See Metonic cycle.
- Coronavirus disease 2019, the cause of the global pandemicthat began in 2019.
- The James Webb Space Telescope's optical elements are in an array of 19 hexagons, wherein 18 segmented primary mirrors focus light into a centered secondary mirror situated above the collecting mirrors, that in-turn reflects back onto the telescope's central imagers. It is a shape akin to the order-3 magic hexagon.
Religion
Islam
- The number of Qur'an: "Over it are nineteen" (74:30), after which the Qur'an describes this number as being "a trial for those who disbelieve" (74:31), a sign for people of the scripture to be "convinced" (74:31) and that believers "will increase in faith" (74:31) due to it.
- The Number of Verse and Sura together in the Qur'an which announces Jesus son of Maryam's (Mary's) birth (Qur'an 19:19).
- A group called United Submitter International claim the Quran has mathematical structure based on the number 19. The gematrical value of WAHD = 6+1+8+4=19, Wahd means 'One' (God) to the first verse (1:1), known as Bas-malah, consists of 19 Arabic letters or the Quran consists of 114 (19x6) surat etc.
Baháʼí faith
In the
- The Baháʼí calendar is structured such that a year contains 19 months of 19 days each (along with the intercalary period of Ayyám-i-Há), as well as a 19-year cycle and a 361-year (19x19) supercycle.
- The Báb and his disciples formed a group of 19.
- There were 19 Apostles of Bahá'u'lláh.
Celtic paganism
19 is a sacred number of the goddess Brigid because it is said to represent the 19-year cycle of the Great Celtic Year and the amount of time it takes the Moon to coincide with the winter solstice.[48]
Music
- "19" is a 1985 song by Paul Hardcastle, including sampled soundbites taken from a documentary about the Vietnam War in which 19 is claimed to have been the average age of United States soldiers killed in the conflict.[49] The song was parodied by British satirist Rory Bremner under the pseudonym 'The Commentators,' as N-n-nineteen, Not Out, the title referring to the batting average of David Gower, the England cricket captain, during his side's risible performance against the West Indies in 1984 when they lost 5–0.
- "I Was Only Nineteen" by the Australian group Redgum reached number one on the Australian charts in 1983. In 2005 a hip hop version of the song was produced by The Herd.
- 19 is the name of Adele's 2008 debut album, so named since she was 19 years old at the time.
- "Hey Nineteen" is a song by American jazz rock band Steely Dan, on the 1980 album Gaucho.
- Nineteen has been used as an alternative to twelve for a division of the octave into equal parts. This idea goes back to meantone tuning, being close to 1/3 comma meantone. See 19 equal temperament.
- Some organs use the 19th harmonic to approximate a minor third.
Literature
- The Wind Through the Keyholeas a mysterious and important number. They refer to the "ka-tet of 19", "Directive Nineteen," many names add up to 19, 19 seems to permeate every aspect of Roland and his traveler's lives. In addition, the number ends up being a powerful key.
- In Jodi Picoult's bestselling book Nineteen Minutes, the number 19 is referenced multiple times. It is most commonly referenced when referring to the main subject of the book, the school shooting rampage that took place over a span of 19 minutes.
- The novel S. by Doug Dorst uses 19 and its multiples throughout. S is the 19th letter of the alphabet.
Games
- The game of Go is played on a grid of 19×19 lines (though variants can be played on grids of other sizes).
- Though the maximum score for a cribbage hand is 29, there is no combination of cards that adds up to 19 points. Many cribbage players, therefore, jokingly refer to a zero-point hand as "a 19 hand".
- In the base version of Settlers of Catanthere are 19 hexagonal pieces that can be randomly or intentionally placed to form the board.
Age 19
- In four countries, 19 is the age of majority.
- In two countries, 19 is the minimum legal drinking age.
- In three countries, 19 is the minimum legal smoking age.
In sports
- In golf, the '19th hole' is the clubhouse bar and in match play, if there is a tie after 18 holes, an extra hole(s) is played. In miniature golf it is an extra hole on which the winner earns an instant prize.
In other fields
- The 19th Amendment to the United States Constitutiongave American women the right to vote.
- The Vietnam War spanned over 19 years, from November 1955 to April 1975.
References
- ^ Sloane, N. J. A. (ed.). "Sequence A046117 (Primes p such that p-6 is also prime. (Upper of a pair of sexy primes.))". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-08-05.
- ^ Sloane, N. J. A. (ed.). "Sequence A006512 (Greater of twin primes.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-08-05.
- ^ Sloane, N. J. A. (ed.). "Sequence A088762 (Numbers n such that (2n-1, 2n+3) is a cousin prime pair.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-08-05.
- ^ Sloane, N. J. A. (ed.). "Sequence A001913 (Full reptend primes: primes with primitive root 10.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-08-05.
- ^ Sloane, N. J. A. (ed.). "Sequence A002426 (Central trinomial coefficients: largest coefficient of (1 + x + x^2)^n.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-08-05.
- ^ "Sloane's A000043 : Mersenne exponents". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
- ^ Sloane, N. J. A. (ed.). "Sequence A007629 (Repfigit (REPetitive FIbonacci-like diGIT) numbers (or Keith numbers).)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-08-05.
- ^ Sloane, N. J. A. (ed.). "Sequence A005900 (Octahedral numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-08-17.
- ^ Sloane, N. J. A. (ed.). "Sequence A002804 ((Presumed) solution to Waring's problem.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-08-05.
- ^ Sloane, N. J. A. "3x+1 problem". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-01-24.
- ^ Sloane, N. J. A. (ed.). "Sequence A006577 (Number of halving and tripling steps to reach 1 in '3x+1' problem, or -1 if 1 is never reached)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-01-24.
- "Table of n, a(n) for n = 1..10000".
- ^ "Sloane's A003173 : Heegner numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
- ^ Sloane, N. J. A. (ed.). "Sequence A111441 (Numbers k such that the sum of the squares of the first k primes is divisible by k)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-06-02.
- ^ a b Sloane, N. J. A. (ed.). "Sequence A060544 (Centered 9-gonal (also known as nonagonal or enneagonal) numbers. Every third triangular number, starting with 1)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-11-30.
- ^ "19". Prime Curios!. Retrieved 2022-08-05.
- ^ Sloane, N. J. A. (ed.). "Sequence A005349 (Niven (or Harshad, or harshad) numbers: numbers that are divisible by the sum of their digits.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-10-11.
- ^ Sloane, N. J. A. (ed.). "Sequence A051624 (12-gonal (or dodecagonal) numbers: a(n) equal to n*(5*n-4).)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-12-21.
- ^ Sloane, N. J. A. (ed.). "Sequence A068174 (Define an increasing sequence as follows. Start with an initial term, the seed (which need not have the property of the sequence); subsequent terms are obtained by inserting/placing at least one digit in the previous term to obtain the smallest number with the given property. Here the property is be a prime.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-07-26.
- ^ Sloane, N. J. A. (ed.). "Sequence A088275 (Numbers n such that 10^n + 9 is prime)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-07-28.
- ISBN 1475717385
- ^ "Sloane's A125602 : Centered triangular numbers that are prime". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
- ^ "Sloane's A003215 : Hex (or centered hexagonal) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
- ^ Sloane, N. J. A. (ed.). "Sequence A000217 (Triangular numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-07-13.
- ^ Sloane, N. J. A. "Sequence A186076". The On-line Encyclopedia of Integer Sequences. Retrieved 2022-07-13.
Note that terms A186074(4) and A186074(10) have trailing 0's, i.e. 19900 = Sum_{k=0..199} k and 1999000 = Sum_{k=0..1999} k...". "This pattern continues indefinitely: 199990000, 19999900000, etc.
- ^ Sloane, N. J. A. (ed.). "Sequence A055558 (Primes of the form 1999...999)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-07-26.
- ^ Sloane, N. J. A. (ed.). "Sequence A007569 (Number of nodes in regular n-gon with all diagonals drawn.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-04-04.
- ^ Trigg, C. W. (February 1964). "A Unique Magic Hexagon". Recreational Mathematics Magazine. Retrieved 2022-07-14.
- S2CID 218544330.
- ^ Sloane, N. J. A. (ed.). "Sequence A006534 (Number of one-sided triangular polyominoes (n-iamonds) with n cells; turning over not allowed, holes are allowed.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-12-08.
- Zbl 1003.05500.
- ^ Sloane, N. J. A. (ed.). "Sequence A072359 (Primes p such that the p-1 digits of the decimal expansion of k/p (for k equal to 1,2,3,...,p-1) fit into the k-th row of a magic square grid of order p-1.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-09-04.
- ^ Sloane, N. J. A. (ed.). "Sequence A000040 (The prime numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-09-06.
- ^ Sloane, N. J. A. (ed.). "Sequence A006003 (a(n) equal to n*(n^2 + 1)/2.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-09-04.
- S2CID 120672023.
- S2CID 14378861.
- Zbl 1062.52012.
- Zbl 1444.14091.
- ^ Sloane, N. J. A. (ed.). "Sequence A002267 (The 15 supersingular primes.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-12-11.
- Zbl 1113.00002.
- Zbl 0914.20016.
- List of standard generators of all sporadic groups.
- Zbl 1087.20025.
- Zbl 1089.20006.
- ^ Sloane, N. J. A. (ed.). "Sequence A000040 (The prime numbers.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2024-02-28.
- ^ Sloane, N. J. A. (ed.). "Sequence A000292". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2024-02-28.
- ^ Sloane, N. J. A. (ed.). "Sequence A051871 (19-gonal (or enneadecagonal) numbers: n(17n-15)/2.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-12-09.
- PMID 28935903.
...so [sic] moonshine illuminates a physical origin for the monster, and for the 19 other sporadic groups that are involved in the monster.
- .
...for all groups of Lie type, including the twisted groups of Steinberg, Suzuki and Ree (and the Tits group).
- ^ Brigid: Triple Goddess of the Flame (Health, Hearth, & Forge)
- ^ Roush, Gary (2008-06-02). "Statistics about the Vietnam War". Vietnam Helicopter Flight Crew Network. Archived from the original on 2010-01-06. Retrieved 2009-12-06.
Assuming KIAs accurately represented age groups serving in Vietnam, the average age of an infantryman (MOS 11B) serving in Vietnam to be 19 years old is a myth, it is actually 22. None of the enlisted grades have an average age of less than 20.