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.
['w', '8035', 'J', '2671', '7509', '1573', '6915', '8569', '345', 'T', 'P', 's', '1341', '7823', '8671', 'm', 'Q', 's', 'N']