Alright, let's work through 6641 times 251 step by step
6641 × 251 = 251 × (6641)
+ 251 × 1 what gives us 251
+ 251 × 40 which equals 10040
+ 251 × 600 that is equal 150600
+ 251 × 6000 yielding 1506000

= 1666891
