1397 x 1397 = ?

$$\eqalign{ & 1397 \times 1397 \cr & = {\left( {1397} \right)^2} \cr & = {\left( {1400 - 3} \right)^2} \cr & = {\left( {1400} \right)^2} + {\left( 3 \right)^2} - \left( {2 \times 1400 \times 3} \right) \cr & = 1960000 + 9 - 8400 \cr & = 1960009 - 8400 \cr & = 1951609 \cr} $$