257 (number)

From Wikipedia, the free encyclopedia

257 is the natural number between 256 and 258. It is also a prime number.

List of numbers — Integers ← 0 100 200 300 400 500 600 700 800 900 →
Ordinal	Two hundred [and] fifty-seven
Cardinal	257th
Factorization	prime number
Roman numeral	CCLVII
Binary	100000001
Hexadecimal	101

[edit] In mathematics

257 is a prime number of the form and therefore a Fermat prime. It is currently the second largest known Fermat prime. And since it is of the form 4n + 1, it is a Pythagorean prime.

It is also an irregular prime, and a long prime (in base 10) and a balanced prime. Since the next prime, 263, is 6 away, 257 is called a sexy prime.

Since 257 + 2 = 259, a semiprime, 257 is a Chen prime. It is also an Eisenstein prime with no imaginary part, and a Pierpont prime.