21331805 has 16 divisors (see below), whose sum is σ = 28080000. Its totient is φ = 15428160.

The previous prime is 21331789. The next prime is 21331819. The reversal of 21331805 is 50813312.

It is not a de Polignac number, because 21331805 - 2⁴ = 21331789 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9971 + ... + 11919.

It is an arithmetic number, because the mean of its divisors is an integer number (1755000).

Almost surely, 2^21331805 is an apocalyptic number.

It is an amenable number.

21331805 is a deficient number, since it is larger than the sum of its proper divisors (6748195).

21331805 is a wasteful number, since it uses less digits than its factorization.

21331805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2164.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21331805 is about 4618.6367036172. The cubic root of 21331805 is about 277.3378865374.

The spelling of 21331805 in words is "twenty-one million, three hundred thirty-one thousand, eight hundred five".