21908900 has 72 divisors (see below), whose sum is σ = 53954880. Its totient is φ = 7655040.

The previous prime is 21908899. The next prime is 21908917. The reversal of 21908900 is 980912.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 24257 + ... + 25143.

Almost surely, 2^21908900 is an apocalyptic number.

21908900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21908900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26977440).

21908900 is an abundant number, since it is smaller than the sum of its proper divisors (32045980).

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

21908900 is a wasteful number, since it uses less digits than its factorization.

21908900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 933 (or 926 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 29.

The square root of 21908900 is about 4680.6943929293. The cubic root of 21908900 is about 279.8166316413.

The spelling of 21908900 in words is "twenty-one million, nine hundred eight thousand, nine hundred".