Which number multiplied by itself will give the output as 12345678987654321 ?

Correct Answer: 11 * 11 = 121 111 * 111 = 12321 what we observe is that the square of the number follows a pattern: 2 1's gives 121 3 1's gives 12321 so to get 12345678987654321 we need to get square of 9 1's(111,111,111)