20931664 has 30 divisors (see below), whose sum is σ = 43920366. Its totient is φ = 9659520.

The previous prime is 20931629. The next prime is 20931667. The reversal of 20931664 is 46613902.

It can be written as a sum of positive squares in 3 ways, for example, as 501264 + 20430400 = 708^2 + 4520^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20931667) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1167 + ... + 6574.

Almost surely, 2^20931664 is an apocalyptic number.

It is an amenable number.

20931664 is an abundant number, since it is smaller than the sum of its proper divisors (22988702).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20931664 is a wasteful number, since it uses less digits than its factorization.

20931664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7775 (or 7756 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 20931664 is about 4575.1135505034. The cubic root of 20931664 is about 275.5928323756.

The spelling of 20931664 in words is "twenty million, nine hundred thirty-one thousand, six hundred sixty-four".