21804657 has 12 divisors (see below), whose sum is σ = 33819696. Its totient is φ = 12459720.

The previous prime is 21804641. The next prime is 21804683. The reversal of 21804657 is 75640812.

It is not a de Polignac number, because 21804657 - 2⁴ = 21804641 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21804637) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 74019 + ... + 74312.

It is an arithmetic number, because the mean of its divisors is an integer number (2818308).

Almost surely, 2^21804657 is an apocalyptic number.

It is an amenable number.

21804657 is a deficient number, since it is larger than the sum of its proper divisors (12015039).

21804657 is a wasteful number, since it uses less digits than its factorization.

21804657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148348 (or 148341 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21804657 is about 4669.5456952470. The cubic root of 21804657 is about 279.3721348094.

The spelling of 21804657 in words is "twenty-one million, eight hundred four thousand, six hundred fifty-seven".