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.
['2073', 'X', 'F', 'Q', '1665', 'U', 'N', 'K', 'w', '6497', '7131', '7143', '5803', 'P', '185', '8883', '7043', '4571', '5447']