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.
['7801', 'e', '7497', 'k', 'O', 'i', '3835', 'S', 'w', '6847', 'X', 't', '1471', 'w', 'o', '9895', 'd', '7177', 'G']