21604866 has 32 divisors (see below), whose sum is σ = 46061568. Its totient is φ = 6739920.

The previous prime is 21604853. The next prime is 21604871. The reversal of 21604866 is 66840612.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4821 + ... + 8151.

It is an arithmetic number, because the mean of its divisors is an integer number (1439424).

Almost surely, 2^21604866 is an apocalyptic number.

21604866 is an abundant number, since it is smaller than the sum of its proper divisors (24456702).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21604866 is a wasteful number, since it uses less digits than its factorization.

21604866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3406.

The product of its (nonzero) digits is 13824, while the sum is 33.

The square root of 21604866 is about 4648.1034842181. The cubic root of 21604866 is about 278.5162413829.

The spelling of 21604866 in words is "twenty-one million, six hundred four thousand, eight hundred sixty-six".