Maths secrets :

• Reverse of squares of 12 and 13 is equal to the squares of 21 and 31 respectively .

             12 x 12  = 144 | 441 = 21 x 21
             13 x 13  = 169 | 961 = 31 x 31

• After 7 all prime numbers end with 1,3,7 or 9 . 

             For eg - 11 , 13 , 17 , 19 , 23 , 29 , 31 , 37 etc

• All squares of numbers are multiples of 4 or multiples of 4 +1 

            For eg - 9 =  4 x 2 + 1
                 16 =  4 x 4
                 25 =  4 x 6 + 1
                 36 =  4 x 9