21187868 has 24 divisors (see below), whose sum is σ = 40183920. Its totient is φ = 9774960.

The previous prime is 21187847. The next prime is 21187871. The reversal of 21187868 is 86878112.

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 7 ways as a sum of consecutive naturals, for example, 7583 + ... + 9993.

It is an arithmetic number, because the mean of its divisors is an integer number (1674330).

Almost surely, 2^21187868 is an apocalyptic number.

It is an amenable number.

21187868 is a deficient number, since it is larger than the sum of its proper divisors (18996052).

21187868 is a wasteful number, since it uses less digits than its factorization.

21187868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2454 (or 2426 counting only the distinct ones).

The product of its digits is 43008, while the sum is 41.

The square root of 21187868 is about 4603.0281337398. The cubic root of 21187868 is about 276.7126963302.

The spelling of 21187868 in words is "twenty-one million, one hundred eighty-seven thousand, eight hundred sixty-eight".