21604465 has 4 divisors (see below), whose sum is σ = 25925364. Its totient is φ = 17283568.

The previous prime is 21604439. The next prime is 21604469. The reversal of 21604465 is 56440612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16834609 + 4769856 = 4103^2 + 2184^2 .

It is a cyclic number.

It is not a de Polignac number, because 21604465 - 2¹¹ = 21602417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21604469) 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 in 3 ways as a sum of consecutive naturals, for example, 2160442 + ... + 2160451.

It is an arithmetic number, because the mean of its divisors is an integer number (6481341).

Almost surely, 2^21604465 is an apocalyptic number.

It is an amenable number.

21604465 is a deficient number, since it is larger than the sum of its proper divisors (4320899).

21604465 is an equidigital number, since it uses as much as digits as its factorization.

21604465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4320898.

The product of its (nonzero) digits is 5760, while the sum is 28.

The square root of 21604465 is about 4648.0603481452. The cubic root of 21604465 is about 278.5145182263.

The spelling of 21604465 in words is "twenty-one million, six hundred four thousand, four hundred sixty-five".