665322561 has 6 divisors (see below), whose sum is σ = 961021490. Its totient is φ = 443548368.

The previous prime is 665322551. The next prime is 665322571. The reversal of 665322561 is 165223566.

It is a happy number.

665322561 is a `hidden beast` number, since 6 + 65 + 32 + 2 + 561 = 666.

It is an interprime number because it is at equal distance from previous prime (665322551) and next prime (665322571).

It can be written as a sum of positive squares in only one way, i.e., 660233025 + 5089536 = 25695^2 + 2256^2 .

It is not a de Polignac number, because 665322561 - 2⁷ = 665322433 is a prime.

It is a super-2 number, since 2×665322561² = 885308220351197442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665322521) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36962356 + ... + 36962373.

Almost surely, 2^665322561 is an apocalyptic number.

It is an amenable number.

665322561 is a deficient number, since it is larger than the sum of its proper divisors (295698929).

665322561 is a wasteful number, since it uses less digits than its factorization.

665322561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73924735 (or 73924732 counting only the distinct ones).

The product of its digits is 64800, while the sum is 36.

The square root of 665322561 is about 25793.8473477688. The cubic root of 665322561 is about 872.9929775103.

The spelling of 665322561 in words is "six hundred sixty-five million, three hundred twenty-two thousand, five hundred sixty-one".