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.
['6653', 'h', 's', '5717', '4517', '7669', 'k', '8889', 'A', '8485', '8985', '5187', 'v', '733', '7343', 'y', 'P', 'O', '6717']