The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

Three logicians went to bar for having a drink. The bar person asks the logicians "Do they all want to have the drink?". The first logician replied, " I don't know". The second logician replied, " I don't know". What is the reply of the last logician?

Decode the below four famous ciphers:

8P of the SS
1M of the E
1S of the SS
60M in 1H

What is both possible and impossible at the same time?

Replace the question mark with the correct number.

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

100 prisoners are stuck in the prison in solitary cells. The warden of the prison got bored one day and offered them a challenge. He will put one prisoner per day, selected at random (a prisoner can be selected more than once), into a special room with a light bulb and a switch which controls the bulb. No other prisoners can see or control the light bulb. The prisoner in the special room can either turn on the bulb, turn off the bulb or do nothing. On any day, the prisoners can stop this process and say "Every prisoner has been in the special room at least once". If that happens to be true, all the prisoners will be set free. If it is false, then all the prisoners will be executed. The prisoners are given some time to discuss and figure out a solution. How do they ensure they all go free?

Can you decipher the following common phrase?

T M C
A U O
H S M
W T E

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

You have 10 balls with you. A friend of yours out of nowhere asks you to place those ten balls in five lines such that each of the lines has exactly 4 balls on them. He needs to check your intelligence. Prove him by doing the task.