Alright, let's work through 1639481 times 64381380 step by step
1639481 × 64381380 = 64381380 × (1639481)
+ 64381380 × 1 what gives us 64381380
+ 64381380 × 80 that results in 5150510400
+ 64381380 × 400 that equals 25752552000
+ 64381380 × 9000 producing 579432420000
+ 64381380 × 30000 what gives us 1931441400000
+ 64381380 × 600000 that is equal 38628828000000
+ 64381380 × 1000000 producing 64381380000000

= 105552049263780
