21929920 has 28 divisors (see below), whose sum is σ = 52221384. Its totient is φ = 8771840.

The previous prime is 21929911. The next prime is 21929959. The reversal of 21929920 is 2992912.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33946 + ... + 34585.

Almost surely, 2^21929920 is an apocalyptic number.

21929920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21929920 is an abundant number, since it is smaller than the sum of its proper divisors (30291464).

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

21929920 is an equidigital number, since it uses as much as digits as its factorization.

21929920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68548 (or 68538 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 34.

The square root of 21929920 is about 4682.9392479510. The cubic root of 21929920 is about 279.9060909564.

The spelling of 21929920 in words is "twenty-one million, nine hundred twenty-nine thousand, nine hundred twenty".