21507328 has 36 divisors (see below), whose sum is σ = 44426340. Its totient is φ = 10379264.

The previous prime is 21507307. The next prime is 21507349. The reversal of 21507328 is 82370512.

It is an interprime number because it is at equal distance from previous prime (21507307) and next prime (21507349).

It can be written as a sum of positive squares in 2 ways, for example, as 6390784 + 15116544 = 2528^2 + 3888^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21507296 and 21507305.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5976 + ... + 8872.

It is an arithmetic number, because the mean of its divisors is an integer number (1234065).

Almost surely, 2^21507328 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 21507328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22213170).

21507328 is an abundant number, since it is smaller than the sum of its proper divisors (22919012).

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

21507328 is an equidigital number, since it uses as much as digits as its factorization.

21507328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2942 (or 2928 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 21507328 is about 4637.5993789891. The cubic root of 21507328 is about 278.0964763577.

The spelling of 21507328 in words is "twenty-one million, five hundred seven thousand, three hundred twenty-eight".