21605604 has 24 divisors (see below), whose sum is σ = 50779680. Its totient is φ = 7149504.

The previous prime is 21605593. The next prime is 21605611. The reversal of 21605604 is 40650612.

21605604 = T₂₄₇ + T₂₄₈ + ... + T₅₂₄.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4809 + ... + 8144.

It is an arithmetic number, because the mean of its divisors is an integer number (2115820).

Almost surely, 2^21605604 is an apocalyptic number.

It is an amenable number.

21605604 is an abundant number, since it is smaller than the sum of its proper divisors (29174076).

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

21605604 is a wasteful number, since it uses less digits than its factorization.

21605604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13099 (or 13097 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21605604 is about 4648.1828707571. The cubic root of 21605604 is about 278.5194126229.

The spelling of 21605604 in words is "twenty-one million, six hundred five thousand, six hundred four".