Alright, let's work through 3878 times 5381 step by step
3878 × 5381 = 5381 × (3878)
+ 5381 × 8 what gives us 43048
+ 5381 × 70 that results in 376670
+ 5381 × 800 producing 4304800
+ 5381 × 3000 yielding 16143000

= 20867518
