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.
['t', '6649', '7685', 'l', 'C', '1317', '533', 'F', '379', '9627', '6165', '7013', 'X', 'N', 'W', 'p', 'x', '9693', 'z', '5557']