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.
['K', 'O', 'p', '1669', '8647', '3417', 'a', '8903', 'V', 'E', 'l', 'a', '5177', 'J', '6559', '5377', 'X', '9427']