665688 has 16 divisors (see below), whose sum is σ = 1664280. Its totient is φ = 221888.

The previous prime is 665677. The next prime is 665713. The reversal of 665688 is 886566.

It is a congruent number.

It is an unprimeable number.

665688 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13845 + ... + 13892.

2⁶⁶⁵⁶⁸⁸ is an apocalyptic number.

It is an amenable number.

665688 is an abundant number, since it is smaller than the sum of its proper divisors (998592).

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

665688 is a wasteful number, since it uses less digits than its factorization.

665688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27746 (or 27742 counting only the distinct ones).

The product of its digits is 69120, while the sum is 39.

The square root of 665688 is about 815.8970523295. The cubic root of 665688 is about 87.3152783348.

The spelling of 665688 in words is "six hundred sixty-five thousand, six hundred eighty-eight".