21972864 has 32 divisors (see below), whose sum is σ = 58366440. Its totient is φ = 7324160.

The previous prime is 21972833. The next prime is 21972869. The reversal of 21972864 is 46827912.

It is a tau number, because it is divible by the number of its divisors (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21972869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28227 + ... + 28994.

Almost surely, 2^21972864 is an apocalyptic number.

21972864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21972864 is an abundant number, since it is smaller than the sum of its proper divisors (36393576).

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

21972864 is an equidigital number, since it uses as much as digits as its factorization.

21972864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57238 (or 57226 counting only the distinct ones).

The product of its digits is 48384, while the sum is 39.

The square root of 21972864 is about 4687.5221599476. The cubic root of 21972864 is about 280.0886793942.

The spelling of 21972864 in words is "twenty-one million, nine hundred seventy-two thousand, eight hundred sixty-four".