Alright, let's work through 6561 times 1000 step by step
6561 × 1000 = 1000 × (6561)
+ 1000 × 1 which equals 1000
+ 1000 × 60 resulting in 60000
+ 1000 × 500 what gives us 500000
+ 1000 × 6000 what gives us 6000000

= 6561000
