Alright, let's work through 8645 times 9121 step by step
8645 × 9121 = 9121 × (8645)
+ 9121 × 5 producing 45605
+ 9121 × 40 what gives us 364840
+ 9121 × 600 giving us 5472600
+ 9121 × 8000 yielding 72968000

= 78851045
