Alright, let's work through 5645 times 3578 step by step
5645 × 3578 = 3578 × (5645)
+ 3578 × 5 producing 17890
+ 3578 × 40 giving us 143120
+ 3578 × 600 which equals 2146800
+ 3578 × 5000 giving us 17890000

= 20197810
