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

which number am I?

Can you find the 09 errors in the picture below?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

It's a 7-letter word.
If we remove 1 letter from it, it remains the same.
If we remove 2 letters from it, it remains the same.
If we remove 3 letters from it, it remains the same.
If we remove all the letters from it, still it remains the same.
What is it?

In the picture given below, can you find out which digit will take place of the question mark?

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

Find the next number in the series.
1 10 24 43 67 ?

Sally lives in a place where six months of the year is mild summer and the temperature drops significantly the other six months. She owns a lake where there is a small island. She wants to build a house on the island and needs to get materials there. She doesn’t have a boat, plane, or anything to transport them to the island. How does Sally solve this problem?

I’m tall when I’m young, and I’m short when I’m old. What am I?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?