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.
['G', 'Z', 'J', 'i', '273', '2229', '6153', '929', '9337', 'N', 'x', '9137', 'u', 'k', '6409', '6051', '9563', '3721', '5843']