Alright, let's work through 6640 times 5865 step by step
6640 × 5865 = 5865 × (6640)
+ 5865 × 0 resulting in 0
+ 5865 × 40 that is equal 234600
+ 5865 × 600 producing 3519000
+ 5865 × 6000 producing 35190000

= 38943600
