Alright, let's work through 78640783 times 53666509 step by step
78640783 × 53666509 = 53666509 × (78640783)
+ 53666509 × 3 resulting in 160999527
+ 53666509 × 80 giving us 4293320720
+ 53666509 × 700 what gives us 37566556300
+ 53666509 × 0000 giving us 0
+ 53666509 × 40000 giving us 2146660360000
+ 53666509 × 600000 resulting in 32199905400000
+ 53666509 × 8000000 yielding 429332072000000
+ 53666509 × 70000000 yielding 3756655630000000

= 4220376288636547
