665563661568 has 720 divisors, whose sum is σ = 2188378152576. Its totient is φ = 199961395200.

The previous prime is 665563661561. The next prime is 665563661597. The reversal of 665563661568 is 865166365566.

It is a happy number.

665563661568 is a `hidden beast` number, since 6 + 6 + 5 + 5 + 6 + 3 + 6 + 61 + 568 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665563661561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 3378495646 + ... + 3378495842.

Almost surely, 2^665563661568 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665563661568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1094189076288).

665563661568 is an abundant number, since it is smaller than the sum of its proper divisors (1522814491008).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

665563661568 is a wasteful number, since it uses less digits than its factorization.

665563661568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 472 (or 449 counting only the distinct ones).

The product of its digits is 139968000, while the sum is 63.

The spelling of 665563661568 in words is "six hundred sixty-five billion, five hundred sixty-three million, six hundred sixty-one thousand, five hundred sixty-eight".