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.
['565', 'L', 'A', '6681', 'x', 'd', 'p', 'r', 'w', 'k', 'F', 's', '753', '2447', '4361', '5531', 'u', '5801', '23']