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.
['a', 'S', 'N', '1905', 'j', '4485', 'G', '6137', 'G', 'e', '1427', '6509', 's', '821', '2119', 'u', 'A', 'p', 'T', 'B']