Always in you, Sometimes on you; If I surround you, I can kill you. What am I?
A girl has as many brothers as sisters, but each brother has only half as many brothers as sisters. How many brothers and sisters are there in the family?
I had an infinite supply of water and 5 litres and 3 litres jars. How would you measure exactly 4 litres in the least number of steps?
What makes this number unique: 8,549,176,320?
When I get multiplied by any number, the sum of the figures in the product is always me. What am I?
I hide my treasure in the ground, my tail is big and fluffy. If you spot me in a tree, please don’t call me scruffy. What am I?
When I got four, I have it none. When I got two, I have it some. When I got none, I have it all. What is it?
You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'. S E Q U E N C _
I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal. Who am I?
I am the fastest animal but cannot climb the tree. What am I?
How many triangles can you count in the figure given?
There is a cryptic organization called Cicada 3301 that posts challenging puzzles online, possibly to recruit codebreakers and linguists.