31210000021 has 2 divisors, whose sum is σ = 31210000022. Its totient is φ = 31210000020.

The previous prime is 31209999901. The next prime is 31210000043. The reversal of 31210000021 is 12000001213.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19570611025 + 11639388996 = 139895^2 + 107886^2 .

It is a cyclic number.

It is not a de Polignac number, because 31210000021 - 2¹⁵ = 31209967253 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31209999962 and 31210000007.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31210000091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15605000010 + 15605000011.

It is an arithmetic number, because the mean of its divisors is an integer number (15605000011).

Almost surely, 2^31210000021 is an apocalyptic number.

It is an amenable number.

31210000021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31210000021 is an equidigital number, since it uses as much as digits as its factorization.

31210000021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12, while the sum is 10.

Adding to 31210000021 its reverse (12000001213), we get a palindrome (43210001234).

The spelling of 31210000021 in words is "thirty-one billion, two hundred ten million, twenty-one", and thus it is an aban number.