21805888 has 28 divisors (see below), whose sum is σ = 46601380. Its totient is φ = 10063872.

The previous prime is 21805877. The next prime is 21805907. The reversal of 21805888 is 88850812.

It can be written as a sum of positive squares in 2 ways, for example, as 5419584 + 16386304 = 2328^2 + 4048^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21805888.

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, 12273 + ... + 13936.

It is an arithmetic number, because the mean of its divisors is an integer number (1664335).

Almost surely, 2^21805888 is an apocalyptic number.

It is an amenable number.

21805888 is an abundant number, since it is smaller than the sum of its proper divisors (24795492).

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

21805888 is a wasteful number, since it uses less digits than its factorization.

21805888 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26234 (or 26224 counting only the distinct ones).

The product of its (nonzero) digits is 40960, while the sum is 40.

The square root of 21805888 is about 4669.6775049247. The cubic root of 21805888 is about 279.3773921057.

The spelling of 21805888 in words is "twenty-one million, eight hundred five thousand, eight hundred eighty-eight".