665985 has 16 divisors (see below), whose sum is σ = 1103040. Its totient is φ = 342720.

The previous prime is 665983. The next prime is 665993. The reversal of 665985 is 589566.

It is not a de Polignac number, because 665985 - 2¹ = 665983 is a prime.

665985 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (665981) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 331 + ... + 1200.

It is an arithmetic number, because the mean of its divisors is an integer number (68940).

2⁶⁶⁵⁹⁸⁵ is an apocalyptic number.

It is an amenable number.

665985 is a deficient number, since it is larger than the sum of its proper divisors (437055).

665985 is a wasteful number, since it uses less digits than its factorization.

665985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1568.

The product of its digits is 64800, while the sum is 39.

The square root of 665985 is about 816.0790402896. The cubic root of 665985 is about 87.3282617855.

The spelling of 665985 in words is "six hundred sixty-five thousand, nine hundred eighty-five".