• 251 can be written using four 4's:
251 is nontrivially palindromic in base 8.
It is a strong prime.
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-251 is a prime.
It is a Sophie Germain prime.
It is a Chen prime.
251 is an undulating number in base 8.
It is a plaindrome in base 12, base 14 and base 15.
It is a nialpdrome in base 16.
It is a good prime.
2251 is an apocalyptic number.
251 is an equidigital number, since it uses as much as digits as its factorization.
251 is an odious number, because the sum of its binary digits is odd.
The square root of 251 is about 15.8429795178. The cubic root of 251 is about 6.3079935487.
Subtracting from 251 its reverse (152), we obtain a palindrome (99).
The spelling of 251 in words is "two hundred fifty-one", and thus it is an aban number.