21120864 has 24 divisors (see below), whose sum is σ = 55442520. Its totient is φ = 7040256.

The previous prime is 21120833. The next prime is 21120893. The reversal of 21120864 is 46802112.

It is a tau number, because it is divible by the number of its divisors (24).

It is a super-2 number, since 2×21120864² = 892181792212992, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 109909 + ... + 110100.

It is an arithmetic number, because the mean of its divisors is an integer number (2310105).

Almost surely, 2^21120864 is an apocalyptic number.

21120864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21120864 is an abundant number, since it is smaller than the sum of its proper divisors (34321656).

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

21120864 is a wasteful number, since it uses less digits than its factorization.

21120864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220022 (or 220014 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21120864 is about 4595.7441182033. The cubic root of 21120864 is about 276.4206984708.

Adding to 21120864 its reverse (46802112), we get a palindrome (67922976).

The spelling of 21120864 in words is "twenty-one million, one hundred twenty thousand, eight hundred sixty-four".