21304404 has 96 divisors (see below), whose sum is σ = 61286400. Its totient is φ = 6346080.

The previous prime is 21304397. The next prime is 21304427. The reversal of 21304404 is 40440312.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 93739 + ... + 93965.

It is an arithmetic number, because the mean of its divisors is an integer number (638400).

Almost surely, 2^21304404 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 21304404, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30643200).

21304404 is an abundant number, since it is smaller than the sum of its proper divisors (39981996).

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

21304404 is a wasteful number, since it uses less digits than its factorization.

21304404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330 (or 322 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21304404 is about 4615.6693989063. The cubic root of 21304404 is about 277.2190875333.

Adding to 21304404 its reverse (40440312), we get a palindrome (61744716).

The spelling of 21304404 in words is "twenty-one million, three hundred four thousand, four hundred four".