Alright, let's work through 66578869 times 64571391 step by step
66578869 × 64571391 = 64571391 × (66578869)
+ 64571391 × 9 what gives us 581142519
+ 64571391 × 60 giving us 3874283460
+ 64571391 × 800 what gives us 51657112800
+ 64571391 × 8000 what gives us 516571128000
+ 64571391 × 70000 which equals 4519997370000
+ 64571391 × 500000 what gives us 32285695500000
+ 64571391 × 6000000 which equals 387428346000000
+ 64571391 × 60000000 producing 3874283460000000

= 4299090182536779
