21088920 has 128 divisors (see below), whose sum is σ = 66781440. Its totient is φ = 5322240.

The previous prime is 21088913. The next prime is 21088943. The reversal of 21088920 is 2988012.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 314727 + ... + 314793.

It is an arithmetic number, because the mean of its divisors is an integer number (521730).

Almost surely, 2^21088920 is an apocalyptic number.

21088920 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 21088920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33390720).

21088920 is an abundant number, since it is smaller than the sum of its proper divisors (45692520).

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

21088920 is a wasteful number, since it uses less digits than its factorization.

21088920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185 (or 181 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 30.

The square root of 21088920 is about 4592.2674138164. The cubic root of 21088920 is about 276.2812717545.

The spelling of 21088920 in words is "twenty-one million, eighty-eight thousand, nine hundred twenty".