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.
['t', 'C', '5289', '1183', 'z', 'm', 'N', '5357', '7197', '5635', '7817', '6951', '6613', 'q', 'e', '1649', '2169', 'P', 'a']