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.
['2045', '499', '3759', '6193', '1837', 'y', 'y', 'w', '5509', '253', 'N', 'i', 'G', '273', '4179', '9465', '4129', 'F', '715']