No problem, we've got 3131 and 6440 to multiply
3131 × 6440 = 6440 × (3131)
+ 6440 × 1 that equals 6440
+ 6440 × 30 yielding 193200
+ 6440 × 100 that equals 644000
+ 6440 × 3000 giving us 19320000

= 20163640
