31813519021 has 2 divisors, whose sum is σ = 31813519022. Its totient is φ = 31813519020.

The previous prime is 31813518977. The next prime is 31813519027. The reversal of 31813519021 is 12091531813.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16107163396 + 15706355625 = 126914^2 + 125325^2 .

It is a cyclic number.

It is not a de Polignac number, because 31813519021 - 2²⁵ = 31779964589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31813519027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15906759510 + 15906759511.

It is an arithmetic number, because the mean of its divisors is an integer number (15906759511).

Almost surely, 2^31813519021 is an apocalyptic number.

It is an amenable number.

31813519021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31813519021 is an equidigital number, since it uses as much as digits as its factorization.

31813519021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480, while the sum is 34.

The spelling of 31813519021 in words is "thirty-one billion, eight hundred thirteen million, five hundred nineteen thousand, twenty-one".