Alright, let's work through 6643 times 609 step by step
6643 × 609 = 609 × (6643)
+ 609 × 3 producing 1827
+ 609 × 40 resulting in 24360
+ 609 × 600 that is equal 365400
+ 609 × 6000 which equals 3654000

= 4045587
