21873564 has 30 divisors (see below), whose sum is σ = 57182664. Its totient is φ = 7291080.

The previous prime is 21873539. The next prime is 21873589. The reversal of 21873564 is 46537812.

21873564 is a `hidden beast` number, since 21 + 8 + 73 + 564 = 666.

It is an interprime number because it is at equal distance from previous prime (21873539) and next prime (21873589).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 33432 + ... + 34079.

Almost surely, 2^21873564 is an apocalyptic number.

It is an amenable number.

21873564 is an abundant number, since it is smaller than the sum of its proper divisors (35309100).

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

21873564 is a wasteful number, since it uses less digits than its factorization.

21873564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67527 (or 67516 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 21873564 is about 4676.9182160906. The cubic root of 21873564 is about 279.6661156252. Note that the first 3 decimals are identical.

The spelling of 21873564 in words is "twenty-one million, eight hundred seventy-three thousand, five hundred sixty-four".