Replace the question mark with the correct number below.

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?

How many letters are in the alphabet?

How many sides does a circle have?

During which month do people sleep the least?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

In the picture, you can see a chess board. On the top left position, the K marks a knight. Now, can you move the knight in a manner that after 63 moves, the knight has been placed at all the squares exactly once excluding the starting square?

What work can one never finish?

I guess 76.8% of readers will like this riddle.

What's the least number of people should read this post?