What number do you get when you multiply all of the numbers on a telephone's number pad?

In a boat, the father of a sailor's son is sitting with the son of the sailor. However, the sailor is not present on the boat.

Can this even be possible?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

What is the next number in this matchsticks series riddle?

How many sides does a circle have?

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

Can you write down eight eights so that they add up to one thousand?

I am first found in caves, now prolific online; I am a depiction, a drawing, a symbol, or sign. I will convey whichever mood you could wish; or for that matter, a fist, flask, or fish. What am I?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?