665959 has 6 divisors (see below), whose sum is σ = 774744. Its totient is φ = 570780.

The previous prime is 665953. The next prime is 665981. The reversal of 665959 is 959566.

665959 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 665959 - 2⁹ = 665447 is a prime.

It is an Ulam number.

It is a Duffinian number.

665959 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665953) 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, 6747 + ... + 6844.

It is an arithmetic number, because the mean of its divisors is an integer number (129124).

2⁶⁶⁵⁹⁵⁹ is an apocalyptic number.

665959 is a deficient number, since it is larger than the sum of its proper divisors (108785).

665959 is a wasteful number, since it uses less digits than its factorization.

665959 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13605 (or 13598 counting only the distinct ones).

The product of its digits is 72900, while the sum is 40.

The square root of 665959 is about 816.0631103046. The cubic root of 665959 is about 87.3271253413.

The spelling of 665959 in words is "six hundred sixty-five thousand, nine hundred fifty-nine".