Alright, let's work through 86784819 times 51390859 step by step
86784819 × 51390859 = 51390859 × (86784819)
+ 51390859 × 9 which equals 462517731
+ 51390859 × 10 that is equal 513908590
+ 51390859 × 800 resulting in 41112687200
+ 51390859 × 4000 that is equal 205563436000
+ 51390859 × 80000 yielding 4111268720000
+ 51390859 × 700000 giving us 35973601300000
+ 51390859 × 6000000 resulting in 308345154000000
+ 51390859 × 80000000 that results in 4111268720000000

= 4459946396569521
