Alright, let's work through 6440 times 3928 step by step
6440 × 3928 = 3928 × (6440)
+ 3928 × 0 what gives us 0
+ 3928 × 40 yielding 157120
+ 3928 × 400 resulting in 1571200
+ 3928 × 6000 what gives us 23568000

= 25296320
