Alright, let's work through 6398990 times 21748790 step by step
6398990 × 21748790 = 21748790 × (6398990)
+ 21748790 × 0 what gives us 0
+ 21748790 × 90 producing 1957391100
+ 21748790 × 900 producing 19573911000
+ 21748790 × 8000 that results in 173990320000
+ 21748790 × 90000 that results in 1957391100000
+ 21748790 × 300000 resulting in 6524637000000
+ 21748790 × 6000000 that equals 130492740000000

= 139170289722100
