21603328 has 66 divisors (see below), whose sum is σ = 46503746. Its totient is φ = 10027008.

The previous prime is 21603317. The next prime is 21603343. The reversal of 21603328 is 82330612.

It can be written as a sum of positive squares in 3 ways, for example, as 9437184 + 12166144 = 3072^2 + 3488^2 .

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 5 ways as a sum of consecutive naturals, for example, 295900 + ... + 295972.

Almost surely, 2^21603328 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 21603328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23251873).

21603328 is an abundant number, since it is smaller than the sum of its proper divisors (24900418).

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

21603328 is an equidigital number, since it uses as much as digits as its factorization.

21603328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127 (or 92 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 21603328 is about 4647.9380374527. The cubic root of 21603328 is about 278.5096322523.

The spelling of 21603328 in words is "twenty-one million, six hundred three thousand, three hundred twenty-eight".