Alright, let's work through 3942 times 5395 step by step
3942 × 5395 = 5395 × (3942)
+ 5395 × 2 resulting in 10790
+ 5395 × 40 giving us 215800
+ 5395 × 900 yielding 4855500
+ 5395 × 3000 resulting in 16185000

= 21267090
