Alright, let's work through 81645702 times 62638975 step by step
81645702 × 62638975 = 62638975 × (81645702)
+ 62638975 × 2 producing 125277950
+ 62638975 × 00 which equals 0
+ 62638975 × 700 what gives us 43847282500
+ 62638975 × 5000 yielding 313194875000
+ 62638975 × 40000 that is equal 2505559000000
+ 62638975 × 600000 that results in 37583385000000
+ 62638975 × 1000000 that results in 62638975000000
+ 62638975 × 80000000 what gives us 5011118000000000

= 5114203086435450
