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.
['2135', 'y', '569', '5735', 'V', '3303', '1215', '599', '6653', '6483', '947', '3829', 'I', 'z', '1375', 'U', 'p', '8413']