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.
['N', 'd', 'B', 'd', '4667', 'Q', '7201', '3811', 'D', '8023', 'k', '1379', '8721', '3527', '6125', 'e', 'n', '2509']