No problem, we've got 6435 and 2136 to multiply
6435 × 2136 = 2136 × (6435)
+ 2136 × 5 what gives us 10680
+ 2136 × 30 resulting in 64080
+ 2136 × 400 what gives us 854400
+ 2136 × 6000 giving us 12816000

= 13745160
