Find the next number in the sequence

1, 2, 6, 21, 88, __?

Different lights make me strange by changing me into different sizes. What am I?

How can you take 2 from 5 and leave 4?

What makes this number unique: 8,549,176,320?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?

What four weights can be used to balance from 1 to 30 pounds?

What does this rebus means ?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

In a football game, Christina defeated Teresa by 2 - 0 but no man from either side scored. How can this be possible?