Alright, let's work through 80036364 times 79860921 step by step
80036364 × 79860921 = 79860921 × (80036364)
+ 79860921 × 4 that results in 319443684
+ 79860921 × 60 producing 4791655260
+ 79860921 × 300 which equals 23958276300
+ 79860921 × 6000 resulting in 479165526000
+ 79860921 × 30000 what gives us 2395827630000
+ 79860921 × 000000 giving us 0
+ 79860921 × 0000000 giving us 0
+ 79860921 × 80000000 giving us 6388873680000000

= 6391777742531244
