Alright, let's work through 81128551 times 51000777 step by step
81128551 × 51000777 = 51000777 × (81128551)
+ 51000777 × 1 that is equal 51000777
+ 51000777 × 50 that is equal 2550038850
+ 51000777 × 500 that equals 25500388500
+ 51000777 × 8000 what gives us 408006216000
+ 51000777 × 20000 that equals 1020015540000
+ 51000777 × 100000 that results in 5100077700000
+ 51000777 × 1000000 that is equal 51000777000000
+ 51000777 × 80000000 resulting in 4080062160000000

= 4137619137884127
