Alright, let's work through 1645 times 5421 step by step
1645 × 5421 = 5421 × (1645)
+ 5421 × 5 that results in 27105
+ 5421 × 40 yielding 216840
+ 5421 × 600 that equals 3252600
+ 5421 × 1000 that equals 5421000

= 8917545
