Alright, let's work through 80064799 times 64878839 step by step
80064799 × 64878839 = 64878839 × (80064799)
+ 64878839 × 9 resulting in 583909551
+ 64878839 × 90 what gives us 5839095510
+ 64878839 × 700 yielding 45415187300
+ 64878839 × 4000 that equals 259515356000
+ 64878839 × 60000 that is equal 3892730340000
+ 64878839 × 000000 giving us 0
+ 64878839 × 0000000 that results in 0
+ 64878839 × 80000000 resulting in 5190307120000000

= 5194511203888361
