21216528 has 60 divisors (see below), whose sum is σ = 59714928. Its totient is φ = 7032000.

The previous prime is 21216497. The next prime is 21216529. The reversal of 21216528 is 82561212.

It is a happy number.

21216528 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 652 + 8 = 666.

It is not an unprimeable number, because it can be changed into a prime (21216529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 35851 + ... + 36437.

Almost surely, 2^21216528 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 21216528, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29857464).

21216528 is an abundant number, since it is smaller than the sum of its proper divisors (38498400).

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

21216528 is a wasteful number, since it uses less digits than its factorization.

21216528 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 852 (or 843 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 21216528 is about 4606.1402497102. The cubic root of 21216528 is about 276.8374062627.

It can be divided in two parts, 2121 and 6528, that added together give a square (8649 = 93²).

The spelling of 21216528 in words is "twenty-one million, two hundred sixteen thousand, five hundred twenty-eight".