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', '5511', '3237', 'E', '4267', 'z', '5409', '1355', 'i', 'C', '5985', 'w', '539', '7395', '5991', 'u', 's', '6553']