21664108 has 6 divisors (see below), whose sum is σ = 37912196. Its totient is φ = 10832052.

The previous prime is 21664081. The next prime is 21664109. The reversal of 21664108 is 80146612.

It is not an unprimeable number, because it can be changed into a prime (21664109) 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 as a sum of consecutive naturals, namely, 2708010 + ... + 2708017.

Almost surely, 2^21664108 is an apocalyptic number.

It is an amenable number.

21664108 is a deficient number, since it is larger than the sum of its proper divisors (16248088).

21664108 is a wasteful number, since it uses less digits than its factorization.

21664108 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5416031 (or 5416029 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 21664108 is about 4654.4718282529. The cubic root of 21664108 is about 278.7705791613.

The spelling of 21664108 in words is "twenty-one million, six hundred sixty-four thousand, one hundred eight".