Can you find the odd number in the following?

2716, 4135, 5321 and 7145

Three men in a cafe order a meal the total cost of which is $15. They each contribute $5. The waiter takes the money to the chef who recognises the three as friends and asks the waiter to return $5 to the men.

The waiter is not only poor at mathematics but dishonest and instead of going to the trouble of splitting the $5 between the three he simply gives them $1 each and pockets the remaining $2 for himself.

Now, each of the men effectively paid $4, the total paid is therefore $12. Add the $2 in the waiters pocket and this comes to $14. Where has the other $1 gone from the original $15?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

If you're 8 feet away from a door and with each move you advance half the distance to the door. How many moves will it take to reach the door?

A man died, leaving $10,000,000 for his widow, 5 sons and 4 daughters. Each daughter received an equal amount, each son received twice as much as a daughter, and the widow received three times as much as a son.

How much did the widow receive?

Complete the given grid with valid words. You can only use the letters AAEEIIMMPPTT.

Hint: The grid reads the same across as down.

A train full of passengers goes through a tunnel. When the train comes out from the other end, there is no single person on the train.

How did it happen?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

What does an Island and the letter T have in common?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?