21117688 has 8 divisors (see below), whose sum is σ = 39595680. Its totient is φ = 10558840.

The previous prime is 21117671. The next prime is 21117697. The reversal of 21117688 is 88671112.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1319848 + ... + 1319863.

It is an arithmetic number, because the mean of its divisors is an integer number (4949460).

Almost surely, 2^21117688 is an apocalyptic number.

It is an amenable number.

21117688 is a deficient number, since it is larger than the sum of its proper divisors (18477992).

21117688 is a wasteful number, since it uses less digits than its factorization.

21117688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2639717 (or 2639713 counting only the distinct ones).

The product of its digits is 5376, while the sum is 34.

The square root of 21117688 is about 4595.3985681331. The cubic root of 21117688 is about 276.4068424065.

The spelling of 21117688 in words is "twenty-one million, one hundred seventeen thousand, six hundred eighty-eight".