Alright, let's work through 8991 times 405 step by step
8991 × 405 = 405 × (8991)
+ 405 × 1 that is equal 405
+ 405 × 90 that is equal 36450
+ 405 × 900 resulting in 364500
+ 405 × 8000 yielding 3240000

= 3641355
