21975864 has 32 divisors (see below), whose sum is σ = 55278720. Its totient is φ = 7280096.

The previous prime is 21975851. The next prime is 21975911. The reversal of 21975864 is 46857912.

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 7 ways as a sum of consecutive naturals, for example, 1267 + ... + 6749.

It is an arithmetic number, because the mean of its divisors is an integer number (1727460).

Almost surely, 2^21975864 is an apocalyptic number.

21975864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21975864 is an abundant number, since it is smaller than the sum of its proper divisors (33302856).

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

21975864 is a wasteful number, since it uses less digits than its factorization.

21975864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5659 (or 5655 counting only the distinct ones).

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

The square root of 21975864 is about 4687.8421475131. The cubic root of 21975864 is about 280.1014258406.

The spelling of 21975864 in words is "twenty-one million, nine hundred seventy-five thousand, eight hundred sixty-four".