Alright, let's work through 81018655 times 86361601 step by step
81018655 × 86361601 = 86361601 × (81018655)
+ 86361601 × 5 resulting in 431808005
+ 86361601 × 50 giving us 4318080050
+ 86361601 × 600 which equals 51816960600
+ 86361601 × 8000 which equals 690892808000
+ 86361601 × 10000 that is equal 863616010000
+ 86361601 × 000000 resulting in 0
+ 86361601 × 1000000 which equals 86361601000000
+ 86361601 × 80000000 yielding 6908928080000000

= 6996900756666655
