The equation x^2 + y^2 = 36 represents a circle with center (0,0) and radius 6.
The equation of a circle with center (h,k) and radius r is given by:
(x - h)^2 + (y - k)^2 = r^2
Comparing this equation to the given equation x^2 + y^2 = 36, we can see that h = 0, k = 0, and r^2 = 36.
Therefore, the center of the circle is (0,0) and the radius is 6.