Alright, let's work through 8405 times 2157 step by step
8405 × 2157 = 2157 × (8405)
+ 2157 × 5 what gives us 10785
+ 2157 × 00 what gives us 0
+ 2157 × 400 resulting in 862800
+ 2157 × 8000 that results in 17256000

= 18129585
