How many bases of x are there such that the number 663 in base x is prime?

663_x  can be written as

6(x)^2 + 6x + 3   =

(3 * 2)(x)^2 + (3*2)x + 3  =

3* (2x^2) + 3 * (2x) + 3  =

3 [ 2x^2 + 2x + 1 ]

Since 3 is a factor  of 663_x.....then this is not prime for any base x  [  where x > 6 ]