It is a happy number.
6665 is nontrivially palindromic in base 6.
It is a sphenic number, since it is the product of 3 distinct primes.
It is a Duffinian number.
6665 is an undulating number in base 6.
It is a Curzon number.
It is a nialpdrome in base 10.
It is a self number, because there is not a number n which added to its sum of digits gives 6665.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 6665.
It is an amenable number.
6665 is a wasteful number, since it uses less digits than its factorization.
6665 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 79.
The square root of 6665 is about 81.6394512475. The cubic root of 6665 is about 18.8191520535.
Subtracting from 6665 its reverse (5666), we obtain a palindrome (999).
The spelling of 6665 in words is "six thousand, six hundred sixty-five".