Alright, let's work through 99781920 times 89975015 step by step
99781920 × 89975015 = 89975015 × (99781920)
+ 89975015 × 0 what gives us 0
+ 89975015 × 20 yielding 1799500300
+ 89975015 × 900 producing 80977513500
+ 89975015 × 1000 yielding 89975015000
+ 89975015 × 80000 which equals 7198001200000
+ 89975015 × 700000 that results in 62982510500000
+ 89975015 × 9000000 yielding 809775135000000
+ 89975015 × 90000000 that equals 8097751350000000

= 8977879748728800
