21189808 has 40 divisors (see below), whose sum is σ = 43497216. Its totient is φ = 9979200.

The previous prime is 21189799. The next prime is 21189821. The reversal of 21189808 is 80898112.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25723 + ... + 26533.

Almost surely, 2^21189808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21189808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21748608).

21189808 is an abundant number, since it is smaller than the sum of its proper divisors (22307408).

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

21189808 is a wasteful number, since it uses less digits than its factorization.

21189808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 913 (or 907 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 37.

The square root of 21189808 is about 4603.2388597595. The cubic root of 21189808 is about 276.7211415128.

The spelling of 21189808 in words is "twenty-one million, one hundred eighty-nine thousand, eight hundred eight".