Alright, let's work through 3506 times 5817 step by step
3506 × 5817 = 5817 × (3506)
+ 5817 × 6 what gives us 34902
+ 5817 × 00 that results in 0
+ 5817 × 500 giving us 2908500
+ 5817 × 3000 that is equal 17451000

= 20394402
