21725228 has 36 divisors (see below), whose sum is σ = 44528400. Its totient is φ = 9247392.

The previous prime is 21725213. The next prime is 21725239. The reversal of 21725228 is 82252712.

It is a self number, because there is not a number n which added to its sum of digits gives 21725228.

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, 38726 + ... + 39282.

It is an arithmetic number, because the mean of its divisors is an integer number (1236900).

Almost surely, 2^21725228 is an apocalyptic number.

21725228 is a gapful number since it is divisible by the number (28) 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 21725228, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22264200).

21725228 is an abundant number, since it is smaller than the sum of its proper divisors (22803172).

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

21725228 is a wasteful number, since it uses less digits than its factorization.

21725228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 774 (or 765 counting only the distinct ones).

The product of its digits is 4480, while the sum is 29.

The square root of 21725228 is about 4661.0329327307. The cubic root of 21725228 is about 279.0324940850.

The spelling of 21725228 in words is "twenty-one million, seven hundred twenty-five thousand, two hundred twenty-eight".