Answer:
Iron roof, glass walls, I burn and burn but never fall. What am I?
Alone I am 24th with a friend I am 20. Another friend and I am unclean.
I am needed for most animals and hardcover books
I am heavy forward but backward I am not. What am I?
I am the building with the most number of stories. What am I?
I am the kind of an ant that's good at math. What am I?