Alright, let's work through 81347689 times 62663120 step by step
81347689 × 62663120 = 62663120 × (81347689)
+ 62663120 × 9 what gives us 563968080
+ 62663120 × 80 resulting in 5013049600
+ 62663120 × 600 yielding 37597872000
+ 62663120 × 7000 what gives us 438641840000
+ 62663120 × 40000 yielding 2506524800000
+ 62663120 × 300000 giving us 18798936000000
+ 62663120 × 1000000 that equals 62663120000000
+ 62663120 × 80000000 that is equal 5013049600000000

= 5097499997529680
