What does this rebus riddle means ?

What is the next number in this series?

4,12,84,3612....

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

What does below chemistry rebus means?

Which letter of the alphabet has the most water?

Bay of Bengal is in which state?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

Why is 6 afraid of 7?