21518928 has 60 divisors (see below), whose sum is σ = 62311860. Its totient is φ = 6924288.

The previous prime is 21518881. The next prime is 21518933. The reversal of 21518928 is 82981512.

It can be written as a sum of positive squares in 2 ways, for example, as 12446784 + 9072144 = 3528^2 + 3012^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21518892 and 21518901.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1600 + ... + 6752.

It is an arithmetic number, because the mean of its divisors is an integer number (1038531).

Almost surely, 2^21518928 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 21518928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31155930).

21518928 is an abundant number, since it is smaller than the sum of its proper divisors (40792932).

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

21518928 is a wasteful number, since it uses less digits than its factorization.

21518928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5196 (or 5187 counting only the distinct ones).

The product of its digits is 11520, while the sum is 36.

The square root of 21518928 is about 4638.8498574539. The cubic root of 21518928 is about 278.1464645808.

The spelling of 21518928 in words is "twenty-one million, five hundred eighteen thousand, nine hundred twenty-eight".