21664708 has 12 divisors (see below), whose sum is σ = 40829740. Its totient is φ = 9999072.

The previous prime is 21664703. The next prime is 21664717. The reversal of 21664708 is 80746612.

It can be written as a sum of positive squares in 2 ways, for example, as 2022084 + 19642624 = 1422^2 + 4432^2 .

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21664703) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 208263 + ... + 208366.

Almost surely, 2^21664708 is an apocalyptic number.

It is an amenable number.

21664708 is a deficient number, since it is larger than the sum of its proper divisors (19165032).

21664708 is a wasteful number, since it uses less digits than its factorization.

21664708 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 416646 (or 416644 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 34.

The square root of 21664708 is about 4654.5362819512. The cubic root of 21664708 is about 278.7731527083.

The spelling of 21664708 in words is "twenty-one million, six hundred sixty-four thousand, seven hundred eight".