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.
['Q', '8037', 'r', 'J', 'N', 'Z', 'z', '1189', 'H', '6555', '61', 'k', 'X', 'd', 'W', '6483', 'J', '8815', 'S', '1731']