21722288 has 60 divisors (see below), whose sum is σ = 49617360. Its totient is φ = 9184896.

The previous prime is 21722279. The next prime is 21722291. The reversal of 21722288 is 88222712.

It is a nude number because it is divisible by every one of its digits.

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, 80618 + ... + 80886.

It is an arithmetic number, because the mean of its divisors is an integer number (826956).

Almost surely, 2^21722288 is an apocalyptic number.

21722288 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 21722288, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24808680).

21722288 is an abundant number, since it is smaller than the sum of its proper divisors (27895072).

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

21722288 is a wasteful number, since it uses less digits than its factorization.

21722288 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 394 (or 381 counting only the distinct ones).

The product of its digits is 7168, while the sum is 32.

The square root of 21722288 is about 4660.7175413234. The cubic root of 21722288 is about 279.0199066829.

The spelling of 21722288 in words is "twenty-one million, seven hundred twenty-two thousand, two hundred eighty-eight".