Alright, let's work through 2172 times 9905 step by step
2172 × 9905 = 9905 × (2172)
+ 9905 × 2 that is equal 19810
+ 9905 × 70 which equals 693350
+ 9905 × 100 giving us 990500
+ 9905 × 2000 which equals 19810000

= 21513660
