21191868 has 30 divisors (see below), whose sum is σ = 55400576. Its totient is φ = 7063848.

The previous prime is 21191857. The next prime is 21191873. The reversal of 21191868 is 86819112.

It is a Harshad number since it is a multiple of its sum of digits (36).

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 9 ways as a sum of consecutive naturals, for example, 32380 + ... + 33027.

Almost surely, 2^21191868 is an apocalyptic number.

It is an amenable number.

21191868 is an abundant number, since it is smaller than the sum of its proper divisors (34208708).

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

21191868 is a wasteful number, since it uses less digits than its factorization.

21191868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65423 (or 65412 counting only the distinct ones).

The product of its digits is 6912, while the sum is 36.

The square root of 21191868 is about 4603.4626098188. The cubic root of 21191868 is about 276.7301085137.

The spelling of 21191868 in words is "twenty-one million, one hundred ninety-one thousand, eight hundred sixty-eight".