21668975 has 6 divisors (see below), whose sum is σ = 26869560. Its totient is φ = 17335160.

The previous prime is 21668963. The next prime is 21669007. The reversal of 21668975 is 57986612.

It is not a de Polignac number, because 21668975 - 2¹⁰ = 21667951 is a prime.

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 5 ways as a sum of consecutive naturals, for example, 433355 + ... + 433404.

It is an arithmetic number, because the mean of its divisors is an integer number (4478260).

Almost surely, 2^21668975 is an apocalyptic number.

21668975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21668975 is a deficient number, since it is larger than the sum of its proper divisors (5200585).

21668975 is an equidigital number, since it uses as much as digits as its factorization.

21668975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 866769 (or 866764 counting only the distinct ones).

The product of its digits is 181440, while the sum is 44.

The square root of 21668975 is about 4654.9946294276. The cubic root of 21668975 is about 278.7914535467.

The spelling of 21668975 in words is "twenty-one million, six hundred sixty-eight thousand, nine hundred seventy-five".