257 (number)

257 (number)

257 is the natural number between 256 and 258. It is also a prime number.Number|number = 257
range = 0 - 1000
cardinal = two hundred [and] fifty-seven
ordinal = th
ordinal_text =
numeral =
factorization = prime
prime =
divisor =
roman = CCLVII
unicode =
greek prefix =
latin prefix =
bin = 100000001
oct = 401
duo = 195
hex = 101

In mathematics

257 is a prime number of the form 2^{2^3}+1 and therefore a Fermat prime. It is currently the second largest known Fermat prime. It is also a Proth prime. And since it is of the form 4"n" + 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.

In other fields

257 is the country calling code for Burundi. See List of country calling codes.


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