21204304 has 80 divisors (see below), whose sum is σ = 50086080. Its totient is φ = 8570880.

The previous prime is 21204251. The next prime is 21204329. The reversal of 21204304 is 40340212.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56662 + ... + 57034.

It is an arithmetic number, because the mean of its divisors is an integer number (626076).

Almost surely, 2^21204304 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 21204304, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25043040).

21204304 is an abundant number, since it is smaller than the sum of its proper divisors (28881776).

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

21204304 is a wasteful number, since it uses less digits than its factorization.

21204304 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 428 (or 422 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 21204304 is about 4604.8131341022. The cubic root of 21204304 is about 276.7842290011.

Adding to 21204304 its reverse (40340212), we get a palindrome (61544516).

The spelling of 21204304 in words is "twenty-one million, two hundred four thousand, three hundred four".