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', 'E', 'n', 'g', '8633', 'H', 'B', '6921', '5407', 'j', '2113', 'u', '7885', '4039', 'w', '1679', '3749', 'u', '5543']