21606904 has 16 divisors (see below), whose sum is σ = 44196120. Its totient is φ = 9821280.

The previous prime is 21606899. The next prime is 21606917. The reversal of 21606904 is 40960612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 122679 + ... + 122854.

Almost surely, 2^21606904 is an apocalyptic number.

It is an amenable number.

21606904 is an abundant number, since it is smaller than the sum of its proper divisors (22589216).

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

21606904 is a wasteful number, since it uses less digits than its factorization.

21606904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245550 (or 245546 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 28.

The square root of 21606904 is about 4648.3227082465. The cubic root of 21606904 is about 278.5249986424.

The spelling of 21606904 in words is "twenty-one million, six hundred six thousand, nine hundred four".