251631120721 has 2 divisors, whose sum is σ = 251631120722. Its totient is φ = 251631120720.

The previous prime is 251631120703. The next prime is 251631120757. The reversal of 251631120721 is 127021136152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 241583063121 + 10048057600 = 491511^2 + 100240^2 .

It is a cyclic number.

It is not a de Polignac number, because 251631120721 - 2¹³ = 251631112529 is a prime.

It is not a weakly prime, because it can be changed into another prime (251631120121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125815560360 + 125815560361.

It is an arithmetic number, because the mean of its divisors is an integer number (125815560361).

Almost surely, 2^251631120721 is an apocalyptic number.

It is an amenable number.

251631120721 is a deficient number, since it is larger than the sum of its proper divisors (1).

251631120721 is an equidigital number, since it uses as much as digits as its factorization.

251631120721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5040, while the sum is 31.

Adding to 251631120721 its reverse (127021136152), we get a palindrome (378652256873).

The spelling of 251631120721 in words is "two hundred fifty-one billion, six hundred thirty-one million, one hundred twenty thousand, seven hundred twenty-one".