Answer:
21 = 3 * 7
48 = 6 * 8 = (2 * 3) * (2 * 2 * 2) = 2^4 * 3
81 = 9 * 9 = (3 * 3) * (3 * 3) = 3^4
56 = 8 * 7 = (2 * 2 * 2) * 7 = 2^3 * 7
63 = 9 * 7 = (3 * 3) * 7 = 3^2 * 7
100 = 10 * 10 = (2 * 5) * (2 * 5) = 2^2 * 5^2
103 = 103
155 = 5 * 31
