Alright, let's work through 3991 times 5839 step by step
3991 × 5839 = 5839 × (3991)
+ 5839 × 1 giving us 5839
+ 5839 × 90 that is equal 525510
+ 5839 × 900 which equals 5255100
+ 5839 × 3000 that is equal 17517000

= 23303449
