664445561 has 32 divisors (see below), whose sum is σ = 802166400. Its totient is φ = 543697920.

The previous prime is 664445557. The next prime is 664445563. The reversal of 664445561 is 165544466.

It is not a de Polignac number, because 664445561 - 2² = 664445557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664445563) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 961226 + ... + 961916.

It is an arithmetic number, because the mean of its divisors is an integer number (25067700).

Almost surely, 2^664445561 is an apocalyptic number.

It is an amenable number.

664445561 is a deficient number, since it is larger than the sum of its proper divisors (137720839).

664445561 is a wasteful number, since it uses less digits than its factorization.

664445561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 969.

The product of its digits is 345600, while the sum is 41.

The square root of 664445561 is about 25776.8415636982. The cubic root of 664445561 is about 872.6092280665.

The spelling of 664445561 in words is "six hundred sixty-four million, four hundred forty-five thousand, five hundred sixty-one".