Alright, let's work through 4006 times 1639 step by step
4006 × 1639 = 1639 × (4006)
+ 1639 × 6 that is equal 9834
+ 1639 × 00 that is equal 0
+ 1639 × 000 producing 0
+ 1639 × 4000 yielding 6556000

= 6565834
