21633664 has 32 divisors (see below), whose sum is σ = 46417140. Its totient is φ = 9984000.

The previous prime is 21633653. The next prime is 21633671. The reversal of 21633664 is 46633612.

It can be written as a sum of positive squares in 2 ways, for example, as 16064064 + 5569600 = 4008^2 + 2360^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4837 + ... + 8164.

Almost surely, 2^21633664 is an apocalyptic number.

It is an amenable number.

21633664 is an abundant number, since it is smaller than the sum of its proper divisors (24783476).

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

21633664 is a wasteful number, since it uses less digits than its factorization.

21633664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13028 (or 13016 counting only the distinct ones).

The product of its digits is 15552, while the sum is 31.

The square root of 21633664 is about 4651.2002751978. The cubic root of 21633664 is about 278.6399349627.

The spelling of 21633664 in words is "twenty-one million, six hundred thirty-three thousand, six hundred sixty-four".