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.
['U', '3653', '7453', '6155', '1775', '2447', 'E', '4583', '5681', 'm', '9179', '7575', '4761', 'M', '1827', 'K', '3433', '3223', 'Q', 'O']