Alright, let's work through 87439907 times 99131907 step by step
87439907 × 99131907 = 99131907 × (87439907)
+ 99131907 × 7 which equals 693923349
+ 99131907 × 00 which equals 0
+ 99131907 × 900 resulting in 89218716300
+ 99131907 × 9000 that is equal 892187163000
+ 99131907 × 30000 yielding 2973957210000
+ 99131907 × 400000 that is equal 39652762800000
+ 99131907 × 7000000 which equals 693923349000000
+ 99131907 × 80000000 yielding 7930552560000000

= 8668084728812649
