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.
['7649', 'R', 'v', '7285', 'O', 'm', 'N', 'j', '2925', '1963', 't', 'E', 'L', 'z', 'e', '7691', '1483', 'Q', 'b', 'm']