Alright, let's work through 2121 times 9505 step by step
2121 × 9505 = 9505 × (2121)
+ 9505 × 1 that is equal 9505
+ 9505 × 20 giving us 190100
+ 9505 × 100 that results in 950500
+ 9505 × 2000 producing 19010000

= 20160105
