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.
['p', '6579', 't', '2581', '1725', '4117', '4603', 'A', '3139', '2011', '935', '1475', 'K', '8399', 'f', '8457', '7225', '7323', '797', 'v']