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

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

Find three numbers such that When we multiply three numbers, we will get the prime numbers. The difference between the second and the first number is equal to the third and second.

What is the largest number you can write with just 3 digits?

Rectify the following equality 101 - 102 = 1 by moving just one digit.

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

which number am I?

If "P" means "-", "Q" means "/", "R" means "+", and "S" means "*" then find the value of the following:

21 Q 7 R 9 S 10 P 13

Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

Which three-digit number, made of consecutive digits, like 567, is 2 less than a cube and 2 more than a square?

A girl is twice as old as her brother and half as old as her father. In 50 years, her brother will be half as old as his father. How old is the daughter now?