21664384 has 32 divisors (see below), whose sum is σ = 49327200. Its totient is φ = 9284352.

The previous prime is 21664373. The next prime is 21664417. The reversal of 21664384 is 48346612.

It is a tau number, because it is divible by the number of its divisors (32).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11194 + ... + 12985.

It is an arithmetic number, because the mean of its divisors is an integer number (1541475).

Almost surely, 2^21664384 is an apocalyptic number.

It is an amenable number.

21664384 is an abundant number, since it is smaller than the sum of its proper divisors (27662816).

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

21664384 is an equidigital number, since it uses as much as digits as its factorization.

21664384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24200 (or 24188 counting only the distinct ones).

The product of its digits is 27648, while the sum is 34.

The square root of 21664384 is about 4654.5014770650. The cubic root of 21664384 is about 278.7717629988.

The spelling of 21664384 in words is "twenty-one million, six hundred sixty-four thousand, three hundred eighty-four".