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.
['s', '3881', 'l', '5271', '9227', 'Z', '5429', '7691', '6127', '6301', '8533', 'T', '233', 'j', '1685', 'F', 'b', '3797', '6633', '7917']