31991812 has 18 divisors (see below), whose sum is σ = 56924574. Its totient is φ = 15729120.

The previous prime is 31991809. The next prime is 31991833. The reversal of 31991812 is 21819913.

It can be written as a sum of positive squares in only one way, i.e., 28047616 + 3944196 = 5296^2 + 1986^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 96487 + ... + 96817.

Almost surely, 2^31991812 is an apocalyptic number.

It is an amenable number.

31991812 is a deficient number, since it is larger than the sum of its proper divisors (24932762).

31991812 is an equidigital number, since it uses as much as digits as its factorization.

31991812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 739 (or 406 counting only the distinct ones).

The product of its digits is 3888, while the sum is 34.

The square root of 31991812 is about 5656.1304794002. The cubic root of 31991812 is about 317.4531296675.

The spelling of 31991812 in words is "thirty-one million, nine hundred ninety-one thousand, eight hundred twelve".