21840928 has 48 divisors (see below), whose sum is σ = 44622144. Its totient is φ = 10517760.

The previous prime is 21840919. The next prime is 21840977. The reversal of 21840928 is 82904812.

It is a super-2 number, since 2×21840928² = 954052271802368, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21840893 and 21840902.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 130701 + ... + 130867.

It is an arithmetic number, because the mean of its divisors is an integer number (929628).

Almost surely, 2^21840928 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21840928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22311072).

21840928 is an abundant number, since it is smaller than the sum of its proper divisors (22781216).

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

21840928 is a wasteful number, since it uses less digits than its factorization.

21840928 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 305 (or 297 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 21840928 is about 4673.4278639988. The cubic root of 21840928 is about 279.5269563725.

The spelling of 21840928 in words is "twenty-one million, eight hundred forty thousand, nine hundred twenty-eight".