When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

He digs out tiny caves and stores gold and silver in them. He also built bridges of silver and made crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs his help, yet many people are afraid to let him help them. Who is he?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

What has many keys but can’t open a single lock?

You Throw The Outside, Cook The Inside
Eat The Outside, Throw The Inside.

What Is It?

How many sides does a circle have?

John was piloting a plane behind a car but was never able to overtake it. Why?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

You enter your friend's room. He is not in his room. Although you see that on the bed there are two dogs, five cats, two giraffes and three pigs. Also, a couple of chickens and ducks are flying in the room.

Calculate the number of legs standing on the floor.