Alright, let's work through 1645 times 3689 step by step
1645 × 3689 = 3689 × (1645)
+ 3689 × 5 that equals 18445
+ 3689 × 40 yielding 147560
+ 3689 × 600 producing 2213400
+ 3689 × 1000 resulting in 3689000

= 6068405
