21003604 has 12 divisors (see below), whose sum is σ = 37135924. Its totient is φ = 10393344.

The previous prime is 21003601. The next prime is 21003637. The reversal of 21003604 is 40630012.

It can be written as a sum of positive squares in 2 ways, for example, as 2924100 + 18079504 = 1710^2 + 4252^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26679 + ... + 27454.

Almost surely, 2^21003604 is an apocalyptic number.

It is an amenable number.

21003604 is a deficient number, since it is larger than the sum of its proper divisors (16132320).

21003604 is a wasteful number, since it uses less digits than its factorization.

21003604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54234 (or 54232 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21003604 is about 4582.9689067241. The cubic root of 21003604 is about 275.9081995333.

Adding to 21003604 its reverse (40630012), we get a palindrome (61633616).

The spelling of 21003604 in words is "twenty-one million, three thousand, six hundred four".