• 204 can be written using four 4's:
204 is nontrivially palindromic in base 16.
204 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a tau number, because it is divible by the number of its divisors (12).
It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.
It is a O'Halloran number.
204 is an undulating number in base 4.
204 is a nontrivial repdigit in base 16.
It is a plaindrome in base 9, base 13 and base 16.
It is a nialpdrome in base 6, base 7, base 15 and base 16.
It is a zygodrome in base 2 and base 16.
It is an unprimeable number.
In principle, a polygon with 204 sides can be constructed with ruler and compass.
204 is the 8-th nonagonal number.
It is an amenable number.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
204 is a wasteful number, since it uses less digits than its factorization.
204 is an evil number, because the sum of its binary digits is even.
The square root of 204 is about 14.2828568571. The cubic root of 204 is about 5.8867653169.
Adding to 204 its reverse (402), we get a palindrome (606).