21668804 has 6 divisors (see below), whose sum is σ = 37920414. Its totient is φ = 10834400.

The previous prime is 21668789. The next prime is 21668807. The reversal of 21668804 is 40886612.

It can be written as a sum of positive squares in only one way, i.e., 11235904 + 10432900 = 3352^2 + 3230^2 .

It is not an unprimeable number, because it can be changed into a prime (21668807) by changing a digit.

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 as a sum of consecutive naturals, namely, 2708597 + ... + 2708604.

It is an arithmetic number, because the mean of its divisors is an integer number (6320069).

Almost surely, 2^21668804 is an apocalyptic number.

It is an amenable number.

21668804 is a deficient number, since it is larger than the sum of its proper divisors (16251610).

21668804 is a wasteful number, since it uses less digits than its factorization.

21668804 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5417205 (or 5417203 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 35.

The square root of 21668804 is about 4654.9762620233. The cubic root of 21668804 is about 278.7907201869.

The spelling of 21668804 in words is "twenty-one million, six hundred sixty-eight thousand, eight hundred four".