21557152 has 36 divisors (see below), whose sum is σ = 43916418. Its totient is φ = 10416000.

The previous prime is 21557143. The next prime is 21557177. The reversal of 21557152 is 25175512.

It can be written as a sum of positive squares in only one way, i.e., 14776336 + 6780816 = 3844^2 + 2604^2 .

It is a super-2 number, since 2×21557152² = 929421604702208, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21557152.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 30402 + ... + 31102.

Almost surely, 2^21557152 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 21557152, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21958209).

21557152 is an abundant number, since it is smaller than the sum of its proper divisors (22359266).

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

21557152 is an equidigital number, since it uses as much as digits as its factorization.

21557152 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 773 (or 734 counting only the distinct ones).

The product of its digits is 3500, while the sum is 28.

The square root of 21557152 is about 4642.9680162586. The cubic root of 21557152 is about 278.3110573764.

The spelling of 21557152 in words is "twenty-one million, five hundred fifty-seven thousand, one hundred fifty-two".