251717644861 has 2 divisors, whose sum is σ = 251717644862. Its totient is φ = 251717644860.

The previous prime is 251717644859. The next prime is 251717644877. The reversal of 251717644861 is 168446717152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 160144832761 + 91572812100 = 400181^2 + 302610^2 .

It is a cyclic number.

It is not a de Polignac number, because 251717644861 - 2¹ = 251717644859 is a prime.

Together with 251717644859, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 251717644799 and 251717644808.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251717644561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125858822430 + 125858822431.

It is an arithmetic number, because the mean of its divisors is an integer number (125858822431).

Almost surely, 2^251717644861 is an apocalyptic number.

It is an amenable number.

251717644861 is a deficient number, since it is larger than the sum of its proper divisors (1).

251717644861 is an equidigital number, since it uses as much as digits as its factorization.

251717644861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2257920, while the sum is 52.

The spelling of 251717644861 in words is "two hundred fifty-one billion, seven hundred seventeen million, six hundred forty-four thousand, eight hundred sixty-one".