21636568 has 16 divisors (see below), whose sum is σ = 41512680. Its totient is φ = 10566528.

The previous prime is 21636557. The next prime is 21636617. The reversal of 21636568 is 86563612.

It is a congruent number.

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 in 3 ways as a sum of consecutive naturals, for example, 31105 + ... + 31792.

Almost surely, 2^21636568 is an apocalyptic number.

It is an amenable number.

21636568 is a deficient number, since it is larger than the sum of its proper divisors (19876112).

21636568 is a wasteful number, since it uses less digits than its factorization.

21636568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62946 (or 62942 counting only the distinct ones).

The product of its digits is 51840, while the sum is 37.

The square root of 21636568 is about 4651.5124422063. The cubic root of 21636568 is about 278.6524021707.

The spelling of 21636568 in words is "twenty-one million, six hundred thirty-six thousand, five hundred sixty-eight".