21857472 has 224 divisors, whose sum is σ = 79654400. Its totient is φ = 5723136.

The previous prime is 21857447. The next prime is 21857489. The reversal of 21857472 is 27475812.

21857472 is a `hidden beast` number, since 2 + 18 + 574 + 72 = 666.

It is a tau number, because it is divible by the number of its divisors (224).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 157179 + ... + 157317.

It is an arithmetic number, because the mean of its divisors is an integer number (355600).

Almost surely, 2^21857472 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 21857472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39827200).

21857472 is an abundant number, since it is smaller than the sum of its proper divisors (57796928).

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

21857472 is a wasteful number, since it uses less digits than its factorization.

21857472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180 (or 164 counting only the distinct ones).

The product of its digits is 31360, while the sum is 36.

The square root of 21857472 is about 4675.1975359336. The cubic root of 21857472 is about 279.5975169703.

The spelling of 21857472 in words is "twenty-one million, eight hundred fifty-seven thousand, four hundred seventy-two".