21009999999931 has 2 divisors, whose sum is σ = 21009999999932. Its totient is φ = 21009999999930.

The previous prime is 21009999999887. The next prime is 21010000000019. The reversal of 21009999999931 is 13999999990012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21009999999931 - 2¹⁵ = 21009999967163 is a prime.

It is a super-2 number, since 2×21009999999931² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21009949999931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504999999965 + 10504999999966.

It is an arithmetic number, because the mean of its divisors is an integer number (10504999999966).

Almost surely, 2^{21009999999931} is an apocalyptic number.

21009999999931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21009999999931 is an equidigital number, since it uses as much as digits as its factorization.

21009999999931 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 258280326, while the sum is 79.

The spelling of 21009999999931 in words is "twenty-one trillion, nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred thirty-one".