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.
['2961', '4509', 'm', '4573', '969', 'A', '5591', 'a', '5509', '2867', '523', 'b', 'W', 'q', 'f', '2555', '6769', 'e', '5649', 'S']