Alright, let's work through 4005 times 1661 step by step
4005 × 1661 = 1661 × (4005)
+ 1661 × 5 that results in 8305
+ 1661 × 00 which equals 0
+ 1661 × 000 what gives us 0
+ 1661 × 4000 yielding 6644000

= 6652305
