Alright, let's work through 3645 times 5519 step by step
3645 × 5519 = 5519 × (3645)
+ 5519 × 5 that equals 27595
+ 5519 × 40 that equals 220760
+ 5519 × 600 producing 3311400
+ 5519 × 3000 yielding 16557000

= 20116755
