21228540 has 48 divisors (see below), whose sum is σ = 62028288. Its totient is φ = 5414464.

The previous prime is 21228533. The next prime is 21228553. The reversal of 21228540 is 4582212.

It is a self number, because there is not a number n which added to its sum of digits gives 21228540.

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, 6312 + ... + 9071.

It is an arithmetic number, because the mean of its divisors is an integer number (1292256).

Almost surely, 2^21228540 is an apocalyptic number.

21228540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21228540 is an abundant number, since it is smaller than the sum of its proper divisors (40799748).

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

21228540 is a wasteful number, since it uses less digits than its factorization.

21228540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15418 (or 15416 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 24.

The square root of 21228540 is about 4607.4439768705. The cubic root of 21228540 is about 276.8896413810.

The spelling of 21228540 in words is "twenty-one million, two hundred twenty-eight thousand, five hundred forty".