Alright, let's work through 1603 times 5405 step by step
1603 × 5405 = 5405 × (1603)
+ 5405 × 3 yielding 16215
+ 5405 × 00 producing 0
+ 5405 × 600 yielding 3243000
+ 5405 × 1000 resulting in 5405000

= 8664215
