31991686 has 12 divisors (see below), whose sum is σ = 48676572. Its totient is φ = 15767124.

The previous prime is 31991683. The next prime is 31991693. The reversal of 31991686 is 68619913.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31991683) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 72655 + ... + 73093.

It is an arithmetic number, because the mean of its divisors is an integer number (4056381).

Almost surely, 2^31991686 is an apocalyptic number.

31991686 is a deficient number, since it is larger than the sum of its proper divisors (16684886).

31991686 is an frugal number, since it uses more digits than its factorization.

31991686 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 963 (or 524 counting only the distinct ones).

The product of its digits is 69984, while the sum is 43.

The square root of 31991686 is about 5656.1193410323. The cubic root of 31991686 is about 317.4527129031.

The spelling of 31991686 in words is "thirty-one million, nine hundred ninety-one thousand, six hundred eighty-six".