77 books
Rows Column
1.) 7 11
2.) 11 7
There are only 2 ways that you can stack 77 books into equal piles. This is not considering the arrangement of each book in each pile.
1 and 77 or 77 and 1 cannot be considered a way to stack 77 books into equal piles because it will only be one pile. There is no comparison or another pile to compare its equality.