21328528 has 60 divisors (see below), whose sum is σ = 46362484. Its totient is φ = 9446400.

The previous prime is 21328501. The next prime is 21328537. The reversal of 21328528 is 82582312.

It can be written as a sum of positive squares in 6 ways, for example, as 16257024 + 5071504 = 4032^2 + 2252^2 .

It is a super-2 number, since 2×21328528² = 909812213293568, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21328528.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 349618 + ... + 349678.

Almost surely, 2^21328528 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 21328528, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23181242).

21328528 is an abundant number, since it is smaller than the sum of its proper divisors (25033956).

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

21328528 is a wasteful number, since it uses less digits than its factorization.

21328528 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164 (or 117 counting only the distinct ones).

The product of its digits is 7680, while the sum is 31.

The square root of 21328528 is about 4618.2819316278. The cubic root of 21328528 is about 277.3236842263.

It can be divided in two parts, 2132 and 8528, that multiplied together give a square (18181696 = 4264²).

The spelling of 21328528 in words is "twenty-one million, three hundred twenty-eight thousand, five hundred twenty-eight".