21939931 has 16 divisors (see below), whose sum is σ = 24408160. Its totient is φ = 19595520.

The previous prime is 21939919. The next prime is 21939937. The reversal of 21939931 is 13993912.

It is a cyclic number.

It is not a de Polignac number, because 21939931 - 2⁹ = 21939419 is a prime.

It is a super-2 number, since 2×21939931² = 962721144569522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21939937) 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, 57700 + ... + 58078.

It is an arithmetic number, because the mean of its divisors is an integer number (1525510).

Almost surely, 2^21939931 is an apocalyptic number.

21939931 is a deficient number, since it is larger than the sum of its proper divisors (2468229).

21939931 is a wasteful number, since it uses less digits than its factorization.

21939931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 526.

The product of its digits is 13122, while the sum is 37.

The square root of 21939931 is about 4684.0080059710. The cubic root of 21939931 is about 279.9486768177.

The spelling of 21939931 in words is "twenty-one million, nine hundred thirty-nine thousand, nine hundred thirty-one".