21808900 has 27 divisors (see below), whose sum is σ = 47426869. Its totient is φ = 8704880.

The previous prime is 21808889. The next prime is 21808921. The reversal of 21808900 is 980812.

The square root of 21808900 is 4670.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 7851204 + 13957696 = 2802^2 + 3736^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 46467 + ... + 46933.

Almost surely, 2^21808900 is an apocalyptic number.

21808900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21808900 is the 4670-th square number.

It is an amenable number.

21808900 is an abundant number, since it is smaller than the sum of its proper divisors (25617969).

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

21808900 is an equidigital number, since it uses as much as digits as its factorization.

21808900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 948 (or 474 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 28.

The cubic root of 21808900 is about 279.3902547778.

The spelling of 21808900 in words is "twenty-one million, eight hundred eight thousand, nine hundred".