Alright, let's work through 86421897 times 61512493 step by step
86421897 × 61512493 = 61512493 × (86421897)
+ 61512493 × 7 producing 430587451
+ 61512493 × 90 yielding 5536124370
+ 61512493 × 800 giving us 49209994400
+ 61512493 × 1000 that results in 61512493000
+ 61512493 × 20000 yielding 1230249860000
+ 61512493 × 400000 giving us 24604997200000
+ 61512493 × 6000000 giving us 369074958000000
+ 61512493 × 80000000 yielding 4920999440000000

= 5316026334259221
