No problem, we've got 6431 and 1398 to multiply
6431 × 1398 = 1398 × (6431)
+ 1398 × 1 which equals 1398
+ 1398 × 30 which equals 41940
+ 1398 × 400 giving us 559200
+ 1398 × 6000 that is equal 8388000

= 8990538
