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.
['z', 'U', '6817', 's', '3731', 'M', 'I', '1095', 'l', '5993', '5207', 'e', 'L', '5361', 'v', 'g', '1963', '4829', '9541', '8261']