21133872 has 100 divisors (see below), whose sum is σ = 63917040. Its totient is φ = 6728832.

The previous prime is 21133867. The next prime is 21133897. The reversal of 21133872 is 27833112.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 29454 + ... + 30162.

Almost surely, 2^21133872 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 21133872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31958520).

21133872 is an abundant number, since it is smaller than the sum of its proper divisors (42783168).

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

21133872 is a wasteful number, since it uses less digits than its factorization.

21133872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 752 (or 737 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21133872 is about 4597.1591227627. The cubic root of 21133872 is about 276.4774345103.

Adding to 21133872 its reverse (27833112), we get a palindrome (48966984).

The spelling of 21133872 in words is "twenty-one million, one hundred thirty-three thousand, eight hundred seventy-two".