21117808 has 30 divisors (see below), whose sum is σ = 43473656. Its totient is φ = 9935616.

The previous prime is 21117799. The next prime is 21117821. The reversal of 21117808 is 80871112.

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 5 ways as a sum of consecutive naturals, for example, 2341 + ... + 6907.

Almost surely, 2^21117808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21117808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21736828).

21117808 is an abundant number, since it is smaller than the sum of its proper divisors (22355848).

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

21117808 is a wasteful number, since it uses less digits than its factorization.

21117808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4609 (or 4586 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 21117808 is about 4595.4116246534. The cubic root of 21117808 is about 276.4073659607.

The spelling of 21117808 in words is "twenty-one million, one hundred seventeen thousand, eight hundred eight".