Alright, let's work through 40080396 times 16007907 step by step
40080396 × 16007907 = 16007907 × (40080396)
+ 16007907 × 6 giving us 96047442
+ 16007907 × 90 resulting in 1440711630
+ 16007907 × 300 producing 4802372100
+ 16007907 × 0000 that is equal 0
+ 16007907 × 80000 that equals 1280632560000
+ 16007907 × 000000 that results in 0
+ 16007907 × 0000000 which equals 0
+ 16007907 × 40000000 that is equal 640316280000000

= 641603251691172
