Alright, let's work through 87023085 times 78831089 step by step
87023085 × 78831089 = 78831089 × (87023085)
+ 78831089 × 5 that results in 394155445
+ 78831089 × 80 resulting in 6306487120
+ 78831089 × 000 giving us 0
+ 78831089 × 3000 resulting in 236493267000
+ 78831089 × 20000 resulting in 1576621780000
+ 78831089 × 000000 resulting in 0
+ 78831089 × 7000000 producing 551817623000000
+ 78831089 × 80000000 which equals 6306487120000000

= 6860124558689565
