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.
['s', '3607', 'p', 'P', '9285', 'J', 'l', '9863', '9823', '2817', 'g', '9751', '599', '2605', 'k', 'Y', 'O', 'U', '9649']