31315631021 has 2 divisors, whose sum is σ = 31315631022. Its totient is φ = 31315631020.

The previous prime is 31315630991. The next prime is 31315631023. The reversal of 31315631021 is 12013651313.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19540125796 + 11775505225 = 139786^2 + 108515^2 .

It is an emirp because it is prime and its reverse (12013651313) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31315631021 - 2³⁴ = 14135761837 is a prime.

Together with 31315631023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31315631023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15657815510 + 15657815511.

It is an arithmetic number, because the mean of its divisors is an integer number (15657815511).

Almost surely, 2^31315631021 is an apocalyptic number.

It is an amenable number.

31315631021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31315631021 is an equidigital number, since it uses as much as digits as its factorization.

31315631021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1620, while the sum is 26.

The spelling of 31315631021 in words is "thirty-one billion, three hundred fifteen million, six hundred thirty-one thousand, twenty-one".