21604636 has 12 divisors (see below), whose sum is σ = 39452112. Its totient is φ = 10332608.

The previous prime is 21604621. The next prime is 21604643. The reversal of 21604636 is 63640612.

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, 117325 + ... + 117508.

It is an arithmetic number, because the mean of its divisors is an integer number (3287676).

Almost surely, 2^21604636 is an apocalyptic number.

It is an amenable number.

21604636 is a deficient number, since it is larger than the sum of its proper divisors (17847476).

21604636 is a wasteful number, since it uses less digits than its factorization.

21604636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 234860 (or 234858 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 28.

The square root of 21604636 is about 4648.0787428786. The cubic root of 21604636 is about 278.5152530413.

The spelling of 21604636 in words is "twenty-one million, six hundred four thousand, six hundred thirty-six".