21455872 has 44 divisors (see below), whose sum is σ = 44804736. Its totient is φ = 10250240.

The previous prime is 21455867. The next prime is 21455873. The reversal of 21455872 is 27855412.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21455873) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23097 + ... + 24007.

Almost surely, 2^21455872 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 21455872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22402368).

21455872 is an abundant number, since it is smaller than the sum of its proper divisors (23348864).

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

21455872 is an equidigital number, since it uses as much as digits as its factorization.

21455872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 954 (or 936 counting only the distinct ones).

The product of its digits is 22400, while the sum is 34.

The square root of 21455872 is about 4632.0483589876. The cubic root of 21455872 is about 277.8745185297.

The spelling of 21455872 in words is "twenty-one million, four hundred fifty-five thousand, eight hundred seventy-two".