257
Wikipedia on Answers.com:
Top
257 (number)
 |
This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2009) |
257 is the natural number between 256 and 258. It is also a prime number.
| 257 | |
|---|---|
| Cardinal | two hundred [and] fifty-seven |
| Ordinal | 257th (two hundred [and] fifty-seventh) |
| Factorization | prime |
| Roman numeral | CCLVII |
| Binary | 1000000012 |
| Octal | 4018 |
| Duodecimal | 19512 |
| Hexadecimal | 10116 |
In mathematics
257 is a prime number of the form 
and therefore a Fermat prime. Thus a regular polygon with 257 sides is constructible with compass and unmarked straightedge. It is currently the second largest known Fermat prime. It is also a Proth 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.
257 is the hypotenuse of a primitive Pythagorean triple: 
In other fields
257 is the country calling code for Burundi. See List of country calling codes.
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Post a question - any question - to the WikiAnswers community:
Copyrights:
Wikipedia on Answers.com
This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article 257 (number).
Read more