Alright, let's work through 20177880 times 3639463 step by step
20177880 × 3639463 = 3639463 × (20177880)
+ 3639463 × 0 producing 0
+ 3639463 × 80 that results in 291157040
+ 3639463 × 800 which equals 2911570400
+ 3639463 × 7000 that is equal 25476241000
+ 3639463 × 70000 yielding 254762410000
+ 3639463 × 100000 that results in 363946300000
+ 3639463 × 0000000 what gives us 0
+ 3639463 × 20000000 that results in 72789260000000

= 73436647678440
