21820920 has 128 divisors (see below), whose sum is σ = 72852480. Its totient is φ = 5184000.

The previous prime is 21820891. The next prime is 21820921. The reversal of 21820920 is 2902812.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820921) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 80385 + ... + 80655.

It is an arithmetic number, because the mean of its divisors is an integer number (569160).

Almost surely, 2^21820920 is an apocalyptic number.

21820920 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 21820920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36426240).

21820920 is an abundant number, since it is smaller than the sum of its proper divisors (51031560).

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

21820920 is a wasteful number, since it uses less digits than its factorization.

21820920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 357 (or 353 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 21820920 is about 4671.2867606260. The cubic root of 21820920 is about 279.4415741028.

The spelling of 21820920 in words is "twenty-one million, eight hundred twenty thousand, nine hundred twenty".