Math puzzle #2 Which number multiplied by itself will give the output as 12345678987654321? View Answer... 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). print