Select the set in which the numbers are related in the same way as are the numbers of the following set.
(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits.)
(21, 225, 9)
(12, 49, 2)
1
(14, 64, 2)
2
(11, 18, 7)
3
(15, 54, 3)
4
(13, 81, 6)