20921880 has 64 divisors (see below), whose sum is σ = 71735040. Its totient is φ = 4781952.

The previous prime is 20921867. The next prime is 20921897. The reversal of 20921880 is 8812902.

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 15 ways as a sum of consecutive naturals, for example, 11614 + ... + 13293.

It is an arithmetic number, because the mean of its divisors is an integer number (1120860).

Almost surely, 2^20921880 is an apocalyptic number.

20921880 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20921880 is an abundant number, since it is smaller than the sum of its proper divisors (50813160).

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

20921880 is a wasteful number, since it uses less digits than its factorization.

20921880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24928 (or 24924 counting only the distinct ones).

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

The square root of 20921880 is about 4574.0441624453. The cubic root of 20921880 is about 275.5498859492.

The spelling of 20921880 in words is "twenty million, nine hundred twenty-one thousand, eight hundred eighty".