665973661 has 8 divisors (see below), whose sum is σ = 700234200. Its totient is φ = 632466240.

The previous prime is 665973647. The next prime is 665973677. The reversal of 665973661 is 166379566.

It can be written as a sum of positive squares in 4 ways, for example, as 24025 + 665949636 = 155^2 + 25806^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 665973661 - 2⁹ = 665973149 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665973601) 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 7 ways as a sum of consecutive naturals, for example, 186466 + ... + 190003.

It is an arithmetic number, because the mean of its divisors is an integer number (87529275).

Almost surely, 2^665973661 is an apocalyptic number.

665973661 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

665973661 is a deficient number, since it is larger than the sum of its proper divisors (34260539).

665973661 is a wasteful number, since it uses less digits than its factorization.

665973661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 376559.

The product of its digits is 1224720, while the sum is 49.

The square root of 665973661 is about 25806.4654883229. The cubic root of 665973661 is about 873.2776616838.

The spelling of 665973661 in words is "six hundred sixty-five million, nine hundred seventy-three thousand, six hundred sixty-one".