21805108 has 12 divisors (see below), whose sum is σ = 41094340. Its totient is φ = 10063872.

The previous prime is 21805079. The next prime is 21805117. The reversal of 21805108 is 80150812.

It can be written as a sum of positive squares in 2 ways, for example, as 3640464 + 18164644 = 1908^2 + 4262^2 .

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 3 ways as a sum of consecutive naturals, for example, 209613 + ... + 209716.

Almost surely, 2^21805108 is an apocalyptic number.

It is an amenable number.

21805108 is a deficient number, since it is larger than the sum of its proper divisors (19289232).

21805108 is a wasteful number, since it uses less digits than its factorization.

21805108 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 419346 (or 419344 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 25.

The square root of 21805108 is about 4669.5939866331. The cubic root of 21805108 is about 279.3740609417.

The spelling of 21805108 in words is "twenty-one million, eight hundred five thousand, one hundred eight".