21900805 has 8 divisors (see below), whose sum is σ = 26307072. Its totient is φ = 17503248.

The previous prime is 21900793. The next prime is 21900821. The reversal of 21900805 is 50800912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21900805 - 2⁵ = 21900773 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21900805.

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 7 ways as a sum of consecutive naturals, for example, 6532 + ... + 9298.

It is an arithmetic number, because the mean of its divisors is an integer number (3288384).

Almost surely, 2^21900805 is an apocalyptic number.

It is an amenable number.

21900805 is a deficient number, since it is larger than the sum of its proper divisors (4406267).

21900805 is a wasteful number, since it uses less digits than its factorization.

21900805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4355.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 21900805 is about 4679.8295909146. The cubic root of 21900805 is about 279.7821647555.

The spelling of 21900805 in words is "twenty-one million, nine hundred thousand, eight hundred five".