21821568 has 32 divisors (see below), whose sum is σ = 57964560. Its totient is φ = 7273728.

The previous prime is 21821567. The next prime is 21821573. The reversal of 21821568 is 86512812.

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

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21821561) 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, 28030 + ... + 28797.

Almost surely, 2^21821568 is an apocalyptic number.

It is an amenable number.

21821568 is an abundant number, since it is smaller than the sum of its proper divisors (36142992).

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

21821568 is an equidigital number, since it uses as much as digits as its factorization.

21821568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56844 (or 56832 counting only the distinct ones).

The product of its digits is 7680, while the sum is 33.

The square root of 21821568 is about 4671.3561200148. The cubic root of 21821568 is about 279.4443401998. Note that the first 3 decimals are identical.

The spelling of 21821568 in words is "twenty-one million, eight hundred twenty-one thousand, five hundred sixty-eight".