221031921 has 16 divisors (see below), whose sum is σ = 338423040. Its totient is φ = 126907920.

The previous prime is 221031917. The next prime is 221031931. The reversal of 221031921 is 129130122.

It is not a de Polignac number, because 221031921 - 2² = 221031917 is a prime.

It is a super-2 number, since 2×221031921² = 97710220201900482, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (221031931) 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, 175635 + ... + 176888.

It is an arithmetic number, because the mean of its divisors is an integer number (21151440).

Almost surely, 2^221031921 is an apocalyptic number.

It is an amenable number.

221031921 is a deficient number, since it is larger than the sum of its proper divisors (117391119).

221031921 is a wasteful number, since it uses less digits than its factorization.

221031921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352556.

The product of its (nonzero) digits is 216, while the sum is 21.

The square root of 221031921 is about 14867.1423279661. The cubic root of 221031921 is about 604.6234671841.

The spelling of 221031921 in words is "two hundred twenty-one million, thirty-one thousand, nine hundred twenty-one".