Alright, let's work through 3984 times 521 step by step
3984 × 521 = 521 × (3984)
+ 521 × 4 giving us 2084
+ 521 × 80 that is equal 41680
+ 521 × 900 what gives us 468900
+ 521 × 3000 producing 1563000

= 2075664
