21557172 has 96 divisors (see below), whose sum is σ = 65228800. Its totient is φ = 5380992.

The previous prime is 21557143. The next prime is 21557177. The reversal of 21557172 is 27175512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21557177) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 20229 + ... + 21267.

Almost surely, 2^21557172 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 21557172, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32614400).

21557172 is an abundant number, since it is smaller than the sum of its proper divisors (43671628).

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

21557172 is a wasteful number, since it uses less digits than its factorization.

21557172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1085 (or 1083 counting only the distinct ones).

The product of its digits is 4900, while the sum is 30.

The square root of 21557172 is about 4642.9701700528. The cubic root of 21557172 is about 278.3111434455.

The spelling of 21557172 in words is "twenty-one million, five hundred fifty-seven thousand, one hundred seventy-two".