Alright, let's work through 4129 times 4091 step by step
4129 × 4091 = 4091 × (4129)
+ 4091 × 9 giving us 36819
+ 4091 × 20 which equals 81820
+ 4091 × 100 that equals 409100
+ 4091 × 4000 that is equal 16364000

= 16891739
