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', 'U', 'V', 'N', 'S', '7831', 'E', '7621', 'M', 'O', 'R', 'h', 'L', '2225', '9231', '6517', 'Z', '7643', 'S', '4447']