21665164 has 6 divisors (see below), whose sum is σ = 37914044. Its totient is φ = 10832580.

The previous prime is 21665143. The next prime is 21665183. The reversal of 21665164 is 46156612.

It is a super-2 number, since 2×21665164² = 938758662293792, which contains 22 as substring.

It is an unprimeable number.

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, 2708142 + ... + 2708149.

Almost surely, 2^21665164 is an apocalyptic number.

It is an amenable number.

21665164 is a deficient number, since it is larger than the sum of its proper divisors (16248880).

21665164 is a wasteful number, since it uses less digits than its factorization.

21665164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5416295 (or 5416293 counting only the distinct ones).

The product of its digits is 8640, while the sum is 31.

The square root of 21665164 is about 4654.5852661650. The cubic root of 21665164 is about 278.7751085723.

The spelling of 21665164 in words is "twenty-one million, six hundred sixty-five thousand, one hundred sixty-four".