1. Choose a number with repeating 3's and a final 6.
2. The square is made up of:
   • the same number of 1's as there are repeating 3's in the number;
   • one 2
   • one fewer 8 than there are repeating 3's;
   • a final 96.

   Example:

1. If the number to be squared is 3336:
2. The square has:

   three 1's (same as
   repeating 3's)     1 1 1
one 2                       2
two 8's (one fewer than
   repeating 3's)             8 8
a final 96                        9 6

3. So the square of 3336 is 11,128,896.

   See the pattern?

1. If the number to be squared is 333336:
2. The square has:

   five 1's (same as
   repeating 3's)   1 1 1 1 1
one 2                         2
four 8's (one fewer than
   repeating 3's)               8 8 8 8
a final 96                              9 6

3. So 333336 × 3333336 = 111,112,888,896.