21604571 has 4 divisors (see below), whose sum is σ = 21613944. Its totient is φ = 21595200.

The previous prime is 21604529. The next prime is 21604579. The reversal of 21604571 is 17540612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21604571 - 2¹⁴ = 21588187 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 21604571.

It is not an unprimeable number, because it can be changed into a prime (21604579) 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 3 ways as a sum of consecutive naturals, for example, 1451 + ... + 6731.

It is an arithmetic number, because the mean of its divisors is an integer number (5403486).

Almost surely, 2^21604571 is an apocalyptic number.

21604571 is a deficient number, since it is larger than the sum of its proper divisors (9373).

21604571 is an equidigital number, since it uses as much as digits as its factorization.

21604571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9372.

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 21604571 is about 4648.0717507371. The cubic root of 21604571 is about 278.5149737261.

The spelling of 21604571 in words is "twenty-one million, six hundred four thousand, five hundred seventy-one".