21087564 has 24 divisors (see below), whose sum is σ = 50792448. Its totient is φ = 6802320.

The previous prime is 21087557. The next prime is 21087569. The reversal of 21087564 is 46578012.

It is not an unprimeable number, because it can be changed into a prime (21087569) 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, 27972 + ... + 28715.

It is an arithmetic number, because the mean of its divisors is an integer number (2116352).

Almost surely, 2^21087564 is an apocalyptic number.

It is an amenable number.

21087564 is an abundant number, since it is smaller than the sum of its proper divisors (29704884).

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

21087564 is a wasteful number, since it uses less digits than its factorization.

21087564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56725 (or 56723 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21087564 is about 4592.1197719572. The cubic root of 21087564 is about 276.2753500757.

The spelling of 21087564 in words is "twenty-one million, eighty-seven thousand, five hundred sixty-four".