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.
['r', '3537', 'T', '3611', 'k', '4983', 'h', '4317', '8727', 'E', '6471', '8465', 'f', '5429', 'T', '2169', '2171', 'P', '6941', 'D']