31688491 has 2 divisors, whose sum is σ = 31688492. Its totient is φ = 31688490.

The previous prime is 31688483. The next prime is 31688509. The reversal of 31688491 is 19488613.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31688491 - 2³ = 31688483 is a prime.

It is not a weakly prime, because it can be changed into another prime (31688441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15844245 + 15844246.

It is an arithmetic number, because the mean of its divisors is an integer number (15844246).

Almost surely, 2^31688491 is an apocalyptic number.

31688491 is a deficient number, since it is larger than the sum of its proper divisors (1).

31688491 is an equidigital number, since it uses as much as digits as its factorization.

31688491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41472, while the sum is 40.

The square root of 31688491 is about 5629.2531476209. The cubic root of 31688491 is about 316.4466624537.

The spelling of 31688491 in words is "thirty-one million, six hundred eighty-eight thousand, four hundred ninety-one".