Alright, let's work through 812778 times 99640015 step by step
812778 × 99640015 = 99640015 × (812778)
+ 99640015 × 8 producing 797120120
+ 99640015 × 70 yielding 6974801050
+ 99640015 × 700 what gives us 69748010500
+ 99640015 × 2000 what gives us 199280030000
+ 99640015 × 10000 which equals 996400150000
+ 99640015 × 800000 yielding 79712012000000

= 80985212111670
