21664604 has 24 divisors (see below), whose sum is σ = 41783280. Its totient is φ = 9765504.

The previous prime is 21664529. The next prime is 21664607. The reversal of 21664604 is 40646612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664607) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2609 + ... + 7080.

It is an arithmetic number, because the mean of its divisors is an integer number (1740970).

Almost surely, 2^21664604 is an apocalyptic number.

It is an amenable number.

21664604 is a deficient number, since it is larger than the sum of its proper divisors (20118676).

21664604 is a wasteful number, since it uses less digits than its factorization.

21664604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9749 (or 9747 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 29.

The square root of 21664604 is about 4654.5251100408. The cubic root of 21664604 is about 278.7727066303.

The spelling of 21664604 in words is "twenty-one million, six hundred sixty-four thousand, six hundred four".