31712809021 has 2 divisors, whose sum is σ = 31712809022. Its totient is φ = 31712809020.

The previous prime is 31712808989. The next prime is 31712809057. The reversal of 31712809021 is 12090821713.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28675696921 + 3037112100 = 169339^2 + 55110^2 .

It is an emirp because it is prime and its reverse (12090821713) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31712809021 - 2⁵ = 31712808989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31712809061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15856404510 + 15856404511.

It is an arithmetic number, because the mean of its divisors is an integer number (15856404511).

Almost surely, 2^31712809021 is an apocalyptic number.

It is an amenable number.

31712809021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31712809021 is an equidigital number, since it uses as much as digits as its factorization.

31712809021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6048, while the sum is 34.

The spelling of 31712809021 in words is "thirty-one billion, seven hundred twelve million, eight hundred nine thousand, twenty-one".