In this task, you are given an input list A. You need to find all the elements of the list that are numbers and calculate their sum.
['i', 'C', '4657', '621', 'k', 'q', '2017', 'c', 'k', 'Q', 'F', '7251', '4067', 'r', 'w', 'X', '4623', 'h', '6273', '2617']