1. Choose a number with repeating 9's and a final 8.
2. The square is made up of:
   • the same number of 9's as there are repeating 9's
   • 6
   • the same number of 0's as there are 9's in the square
   • A final 4

   Example:

1. If the number to be squared is 9998:
2. The square has:

   same number of 9's as there are
   repeating 9's:              9 9 9
    6                                6
same number of 0's as 9's
   in the square                       0 0 0
a final 4                                    4

3. So 9998 × 9998 = 99,960,004.

   See the pattern?

1. If the number to be squared is 999998:
2. The square has:

   same number of 9's as there are
   repeating 9's:        9 9 9 9 9
    6                              6
same number of 0's as 9's
   in the square                     0 0 0 0 0
a final 4                                      4

3. So 999997 × 999997 = 999,996,000,004.