21918864 has 40 divisors (see below), whose sum is σ = 61772832. Its totient is φ = 6641920.

The previous prime is 21918859. The next prime is 21918877. The reversal of 21918864 is 46881912.

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 7 ways as a sum of consecutive naturals, for example, 20229 + ... + 21284.

Almost surely, 2^21918864 is an apocalyptic number.

21918864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21918864 is an abundant number, since it is smaller than the sum of its proper divisors (39853968).

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

21918864 is a wasteful number, since it uses less digits than its factorization.

21918864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41535 (or 41529 counting only the distinct ones).

The product of its digits is 27648, while the sum is 39.

The square root of 21918864 is about 4681.7586439286. The cubic root of 21918864 is about 279.8590446996.

The spelling of 21918864 in words is "twenty-one million, nine hundred eighteen thousand, eight hundred sixty-four".