257 (number)

257 (two hundred [and] fifty-seven) is the natural number following 256 and preceding 258.

257 is a prime number of the form ${\displaystyle 2^{2^{n}}+1,}$ specifically with n = 3, and therefore a

Analogously, 257 is the third

Sierpinski prime of the first kind

, of the form ${\displaystyle n^{n}+1}$ ➜ ${\displaystyle 4^{4}+1=257}$.

It is also a balanced prime,^[3] an

Four-fold 257 is