31920881 has 4 divisors (see below), whose sum is σ = 32112192. Its totient is φ = 31729572.

The previous prime is 31920871. The next prime is 31920907. The reversal of 31920881 is 18802913.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 31920881 - 2¹⁴ = 31904497 is a prime.

It is a super-2 number, since 2×31920881² = 2037885287632322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (31920821) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 95405 + ... + 95738.

It is an arithmetic number, because the mean of its divisors is an integer number (8028048).

Almost surely, 2^31920881 is an apocalyptic number.

It is an amenable number.

31920881 is a deficient number, since it is larger than the sum of its proper divisors (191311).

31920881 is a wasteful number, since it uses less digits than its factorization.

31920881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191310.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 31920881 is about 5649.8567238471. The cubic root of 31920881 is about 317.2183411541.

The spelling of 31920881 in words is "thirty-one million, nine hundred twenty thousand, eight hundred eighty-one".