21668842 has 12 divisors (see below), whose sum is σ = 35196390. Its totient is φ = 10000848.

The previous prime is 21668839. The next prime is 21668851. The reversal of 21668842 is 24886612.

It can be written as a sum of positive squares in 3 ways, for example, as 17901361 + 3767481 = 4231^2 + 1941^2 .

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, 31717 + ... + 32392.

Almost surely, 2^21668842 is an apocalyptic number.

21668842 is a deficient number, since it is larger than the sum of its proper divisors (13527548).

21668842 is a wasteful number, since it uses less digits than its factorization.

21668842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64137 (or 64124 counting only the distinct ones).

The product of its digits is 36864, while the sum is 37.

The square root of 21668842 is about 4654.9803436749. The cubic root of 21668842 is about 278.7908831561.

The spelling of 21668842 in words is "twenty-one million, six hundred sixty-eight thousand, eight hundred forty-two".