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.
['2097', '7815', 'f', '1705', '7553', 'C', 'n', '7091', '1253', 'z', '9229', 'H', 'N', '6481', 'H', 'M', 'G', '4527', '8537']