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.
['1217', '3249', '145', '6073', 'W', '1195', 'P', '3775', '365', '6233', '3281', '5247', '8391', 'N', 'e', '6439', '8747', 'w', '1133']