How can you make number one disappear by adding something to it?

What is next number in the pattern below:

131 517 192 123 ?

How far can you walk into the woods?

On my way to St. Ives I saw a man with 7 wives. Each wife had 7 sacks. Each sack had 7 cats. Each cat had 7 kittens. Kittens, cats, sacks, wives. How many were going to St. Ives?

You have a basket containing ten apples. You have ten friends, who each desire an apple. You give each of your friends one apple.
Now all your friends have one apple each, yet there is an apple remaining in the basket.
How?

Who is that with a neck and no head, two arms and no hands? What is it?

There once were seven dwarfs who were all brothers. They were all born two years apart. The youngest dwarf is seven years old. How old is his oldest brother?

How can a man go eight days without sleep?

Can you find out the remainder when 3^300 is divided by 5?

In the given figure, move three matchsticks so that the resulting figure contains two rectangles.