Alright, let's work through 1663 times 3681 step by step
1663 × 3681 = 3681 × (1663)
+ 3681 × 3 producing 11043
+ 3681 × 60 that results in 220860
+ 3681 × 600 what gives us 2208600
+ 3681 × 1000 that equals 3681000

= 6121503
