No problem, we've got 1640 and 4687 to multiply
1640 × 4687 = 4687 × (1640)
+ 4687 × 0 giving us 0
+ 4687 × 40 yielding 187480
+ 4687 × 600 yielding 2812200
+ 4687 × 1000 what gives us 4687000

= 7686680
