21957920 has 96 divisors (see below), whose sum is σ = 56609280. Its totient is φ = 8017920.

The previous prime is 21957917. The next prime is 21957961. The reversal of 21957920 is 2975912.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 94124 + ... + 94356.

It is an arithmetic number, because the mean of its divisors is an integer number (589680).

Almost surely, 2^21957920 is an apocalyptic number.

21957920 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 21957920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28304640).

21957920 is an abundant number, since it is smaller than the sum of its proper divisors (34651360).

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

21957920 is a wasteful number, since it uses less digits than its factorization.

21957920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 298 (or 290 counting only the distinct ones).

The product of its (nonzero) digits is 11340, while the sum is 35.

The square root of 21957920 is about 4685.9278696967. The cubic root of 21957920 is about 280.0251678058.

The spelling of 21957920 in words is "twenty-one million, nine hundred fifty-seven thousand, nine hundred twenty".