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.
['o', 'c', 'D', '735', 'v', '7457', 'B', '9947', '3291', '9945', '3473', 'w', 'y', 'C', 'i', '5427', '611', '4567', 'N', '4645']