21909688 has 16 divisors (see below), whose sum is σ = 41310360. Its totient is φ = 10893600.

The previous prime is 21909673. The next prime is 21909691. The reversal of 21909688 is 88690912.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

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, 6118 + ... + 9013.

Almost surely, 2^21909688 is an apocalyptic number.

It is an amenable number.

21909688 is a deficient number, since it is larger than the sum of its proper divisors (19400672).

21909688 is a wasteful number, since it uses less digits than its factorization.

21909688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15318 (or 15314 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 43.

The square root of 21909688 is about 4680.7785677171. The cubic root of 21909688 is about 279.8199863338.

The spelling of 21909688 in words is "twenty-one million, nine hundred nine thousand, six hundred eighty-eight".