21285320 has 64 divisors (see below), whose sum is σ = 57628800. Its totient is φ = 6912000.

The previous prime is 21285317. The next prime is 21285331. The reversal of 21285320 is 2358212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3320 + ... + 7320.

It is an arithmetic number, because the mean of its divisors is an integer number (900450).

Almost surely, 2^21285320 is an apocalyptic number.

21285320 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 21285320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28814400).

21285320 is an abundant number, since it is smaller than the sum of its proper divisors (36343480).

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

21285320 is a wasteful number, since it uses less digits than its factorization.

21285320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4038 (or 4034 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21285320 is about 4613.6016299633. The cubic root of 21285320 is about 277.1362872894.

The spelling of 21285320 in words is "twenty-one million, two hundred eighty-five thousand, three hundred twenty".