21183920 has 80 divisors (see below), whose sum is σ = 53300160. Its totient is φ = 7805952.

The previous prime is 21183919. The next prime is 21183923. The reversal of 21183920 is 2938112.

It is a tau number, because it is divible by the number of its divisors (80).

It is a self number, because there is not a number n which added to its sum of digits gives 21183920.

It is not an unprimeable number, because it can be changed into a prime (21183923) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53162 + ... + 53558.

It is an arithmetic number, because the mean of its divisors is an integer number (666252).

Almost surely, 2^21183920 is an apocalyptic number.

21183920 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 21183920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26650080).

21183920 is an abundant number, since it is smaller than the sum of its proper divisors (32116240).

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

21183920 is a wasteful number, since it uses less digits than its factorization.

21183920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 462 (or 456 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21183920 is about 4602.5992656324. The cubic root of 21183920 is about 276.6955083560.

The spelling of 21183920 in words is "twenty-one million, one hundred eighty-three thousand, nine hundred twenty".