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.
['4173', 's', 'v', '2007', '1723', 'l', 'N', '6419', '873', '5289', '9457', 'I', 'U', '1291', '9271', '2507', '8553', '6827', 'v', '9875']