• 664 can be written using four 4's:
664 is nontrivially palindromic in base 12.
It is a tau number, because it is divible by the number of its divisors (8).
664 is an undulating number in base 12.
It is a plaindrome in base 14.
It is a nialpdrome in base 10 and base 11.
It is a congruent number.
2664 is an apocalyptic number.
It is an amenable number.
664 is a wasteful number, since it uses less digits than its factorization.
664 is an evil number, because the sum of its binary digits is even.
The square root of 664 is about 25.7681974535. The cubic root of 664 is about 8.7241413429.
Adding to 664 its product of digits (144), we get a palindrome (808).
The spelling of 664 in words is "six hundred sixty-four", and thus it is an aban number.