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.
['6379', 'o', '5815', '3723', 'k', 'a', 'T', '3565', '3149', 'e', '2435', '6447', 'N', 'O', '6723', '3389', '2071']