21805492 has 12 divisors (see below), whose sum is σ = 40404420. Its totient is φ = 10261376.

The previous prime is 21805489. The next prime is 21805507. The reversal of 21805492 is 29450812.

It can be written as a sum of positive squares in 2 ways, for example, as 19749136 + 2056356 = 4444^2 + 1434^2 .

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 3 ways as a sum of consecutive naturals, for example, 160267 + ... + 160402.

It is an arithmetic number, because the mean of its divisors is an integer number (3367035).

Almost surely, 2^21805492 is an apocalyptic number.

It is an amenable number.

21805492 is a deficient number, since it is larger than the sum of its proper divisors (18598928).

21805492 is a wasteful number, since it uses less digits than its factorization.

21805492 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320690 (or 320688 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 21805492 is about 4669.6351035172. The cubic root of 21805492 is about 279.3757009093.

The spelling of 21805492 in words is "twenty-one million, eight hundred five thousand, four hundred ninety-two".