31989921 has 16 divisors (see below), whose sum is σ = 43380288. Its totient is φ = 20966400.

The previous prime is 31989917. The next prime is 31989959. The reversal of 31989921 is 12998913.

It is not a de Polignac number, because 31989921 - 2² = 31989917 is a prime.

It is not an unprimeable number, because it can be changed into a prime (31984921) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 61141 + ... + 61661.

It is an arithmetic number, because the mean of its divisors is an integer number (2711268).

Almost surely, 2^31989921 is an apocalyptic number.

It is an amenable number.

31989921 is a deficient number, since it is larger than the sum of its proper divisors (11390367).

31989921 is a wasteful number, since it uses less digits than its factorization.

31989921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 832.

The product of its digits is 34992, while the sum is 42.

The square root of 31989921 is about 5655.9633131766. The cubic root of 31989921 is about 317.4468747785.

The spelling of 31989921 in words is "thirty-one million, nine hundred eighty-nine thousand, nine hundred twenty-one".