Alright, let's work through 81423618 times 51639552 step by step
81423618 × 51639552 = 51639552 × (81423618)
+ 51639552 × 8 producing 413116416
+ 51639552 × 10 that results in 516395520
+ 51639552 × 600 giving us 30983731200
+ 51639552 × 3000 that results in 154918656000
+ 51639552 × 20000 resulting in 1032791040000
+ 51639552 × 400000 what gives us 20655820800000
+ 51639552 × 1000000 producing 51639552000000
+ 51639552 × 80000000 that is equal 4131164160000000

= 4204679155739136
