257 (number)
From Wikipedia, the free encyclopedia
257 is the natural number between 256 and 258. It is also a prime number.
| 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.
