Alright, let's work through 86346921 times 7740799 step by step
86346921 × 7740799 = 7740799 × (86346921)
+ 7740799 × 1 giving us 7740799
+ 7740799 × 20 that equals 154815980
+ 7740799 × 900 giving us 6966719100
+ 7740799 × 6000 producing 46444794000
+ 7740799 × 40000 producing 309631960000
+ 7740799 × 300000 resulting in 2322239700000
+ 7740799 × 6000000 that results in 46444794000000
+ 7740799 × 80000000 which equals 619263920000000

= 668394159729879
