A cube has six square sides. Supposing that the length of each edge of the sides is s, then the area of each side is s^2. Multiplying that by 6 gives the total surface area of the cube: A = 6s^2.
We are told that the side length is 13sqrt(5). Thus, substitute this value for s in A = 6s^2. Since s=13sqrt(5), A = 6 (13sqrt(5))^2, or 6 (169) (5), or 30(169) square units. Simplify this by multiplying 169 by 30.