21518664 has 32 divisors (see below), whose sum is σ = 54108000. Its totient is φ = 7131392.

The previous prime is 21518647. The next prime is 21518669. The reversal of 21518664 is 46681512.

It is not an unprimeable number, because it can be changed into a prime (21518669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1792 + ... + 6800.

It is an arithmetic number, because the mean of its divisors is an integer number (1690875).

Almost surely, 2^21518664 is an apocalyptic number.

21518664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21518664 is an abundant number, since it is smaller than the sum of its proper divisors (32589336).

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

21518664 is a wasteful number, since it uses less digits than its factorization.

21518664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5197 (or 5193 counting only the distinct ones).

The product of its digits is 11520, while the sum is 33.

The square root of 21518664 is about 4638.8214020374. The cubic root of 21518664 is about 278.1453271176.

The spelling of 21518664 in words is "twenty-one million, five hundred eighteen thousand, six hundred sixty-four".