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.
['385', '4387', '5237', '9831', 'E', '1425', 'G', '9523', '6537', 'T', '1215', 'C', 'M', '1605', '6555', 'p', '7553', 'K', '1839']