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.
['c', 'r', 'R', 'a', '6915', 'C', '3651', 'j', 'L', '9761', '2923', 'Z', 'e', '833', 'W', '1867', 'G', 'H', 'T']