21604942 has 16 divisors (see below), whose sum is σ = 33728400. Its totient is φ = 10366720.

The previous prime is 21604939. The next prime is 21604949. The reversal of 21604942 is 24940612.

It is a self number, because there is not a number n which added to its sum of digits gives 21604942.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21604949) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9342 + ... + 11422.

It is an arithmetic number, because the mean of its divisors is an integer number (2108025).

Almost surely, 2^21604942 is an apocalyptic number.

21604942 is a deficient number, since it is larger than the sum of its proper divisors (12123458).

21604942 is a wasteful number, since it uses less digits than its factorization.

21604942 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2291.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 21604942 is about 4648.1116595882. Note that the first 3 decimals coincide. The cubic root of 21604942 is about 278.5165679638.

The spelling of 21604942 in words is "twenty-one million, six hundred four thousand, nine hundred forty-two".