21587964 has 12 divisors (see below), whose sum is σ = 50371944. Its totient is φ = 7195984.

The previous prime is 21587963. The next prime is 21587987. The reversal of 21587964 is 46978512.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21587963) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 899487 + ... + 899510.

It is an arithmetic number, because the mean of its divisors is an integer number (4197662).

Almost surely, 2^21587964 is an apocalyptic number.

It is an amenable number.

21587964 is an abundant number, since it is smaller than the sum of its proper divisors (28783980).

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

21587964 is a wasteful number, since it uses less digits than its factorization.

21587964 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1799004 (or 1799002 counting only the distinct ones).

The product of its digits is 120960, while the sum is 42.

The square root of 21587964 is about 4646.2849675843. The cubic root of 21587964 is about 278.4435924769.

The spelling of 21587964 in words is "twenty-one million, five hundred eighty-seven thousand, nine hundred sixty-four".