21305804 has 24 divisors (see below), whose sum is σ = 41451648. Its totient is φ = 9515520.

The previous prime is 21305789. The next prime is 21305839. The reversal of 21305804 is 40850312.

It is a self number, because there is not a number n which added to its sum of digits gives 21305804.

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, 4997 + ... + 8220.

It is an arithmetic number, because the mean of its divisors is an integer number (1727152).

Almost surely, 2^21305804 is an apocalyptic number.

It is an amenable number.

21305804 is a deficient number, since it is larger than the sum of its proper divisors (20145844).

21305804 is a wasteful number, since it uses less digits than its factorization.

21305804 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13265 (or 13263 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21305804 is about 4615.8210537238. The cubic root of 21305804 is about 277.2251598024.

The spelling of 21305804 in words is "twenty-one million, three hundred five thousand, eight hundred four".