Alright, let's work through 84711989 times 78510831 step by step
84711989 × 78510831 = 78510831 × (84711989)
+ 78510831 × 9 which equals 706597479
+ 78510831 × 80 what gives us 6280866480
+ 78510831 × 900 which equals 70659747900
+ 78510831 × 1000 that is equal 78510831000
+ 78510831 × 10000 that equals 785108310000
+ 78510831 × 700000 yielding 54957581700000
+ 78510831 × 4000000 giving us 314043324000000
+ 78510831 × 80000000 that equals 6280866480000000

= 6650808652052859
