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

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

John, a 5-year-old boy, was really fond of the chocolates. He asked his Mother to give him some money to buy his favourite chocolates. His Mother gave him $45. He went to the shopkeeper and asked, "How much is one chocolate for?". The shopkeeper said $3 for one chocolate. Also, if you give me the wrappers of three chocolates, I will give you one for the exchange.
In total, how much chocolate could John eat?

I am white when I am dirty, and black when I am clean. What am I?

You are given a set of weighing scales and 12 marbles. The scales are of the old balance variety. That is, a small dish hangs from each end of a rod that is balanced in the middle. The device enables you to conclude either that the contents of the dishes weigh the same or that the dish that falls lower has heavier contents than the other. The 12 marbles appear to be identical. 11 of them are identical, and one is of a different weight. Your task is to identify the unusual marble and discard it. You are allowed to use the scales three times if you wish, but no more. Note that the unusual marble may be heavier or lighter than the others. You are asked to both identify it and determine whether it is heavy or light

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

Ten coins have been arranged as you can see in the given picture. In this arrangement, a triangle is formed pointing upwards. You have to invert the position of the triangle and make it point downwards while changing the position of 3 coins only. Can you do it?

What is the centre of gravity?

I am never scared but became petrified and can’t live in a house but would die to make one. What am I?

Can you guess the name of the month by looking the below rebus ?