31621921 has 16 divisors (see below), whose sum is σ = 34461504. Its totient is φ = 28905984.

The previous prime is 31621901. The next prime is 31621949. The reversal of 31621921 is 12912613.

It is not a de Polignac number, because 31621921 - 2²¹ = 29524769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31621901) 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, 102850 + ... + 103156.

It is an arithmetic number, because the mean of its divisors is an integer number (2153844).

Almost surely, 2^31621921 is an apocalyptic number.

It is an amenable number.

31621921 is a deficient number, since it is larger than the sum of its proper divisors (2839583).

31621921 is a wasteful number, since it uses less digits than its factorization.

31621921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480.

The product of its digits is 648, while the sum is 25.

The square root of 31621921 is about 5623.3371764460. The cubic root of 31621921 is about 316.2249139855.

The spelling of 31621921 in words is "thirty-one million, six hundred twenty-one thousand, nine hundred twenty-one".