21004404 has 24 divisors (see below), whose sum is σ = 49113120. Its totient is φ = 6986784.

The previous prime is 21004387. The next prime is 21004447. The reversal of 21004404 is 40440012.

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 7 ways as a sum of consecutive naturals, for example, 5202 + ... + 8310.

It is an arithmetic number, because the mean of its divisors is an integer number (2046380).

Almost surely, 2^21004404 is an apocalyptic number.

It is an amenable number.

21004404 is an abundant number, since it is smaller than the sum of its proper divisors (28108716).

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

21004404 is a wasteful number, since it uses less digits than its factorization.

21004404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3679 (or 3677 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21004404 is about 4583.0561855600. The cubic root of 21004404 is about 275.9117024838.

Adding to 21004404 its reverse (40440012), we get a palindrome (61444416).

The spelling of 21004404 in words is "twenty-one million, four thousand, four hundred four".