Alright, let's work through 6420 times 3594 step by step
6420 × 3594 = 3594 × (6420)
+ 3594 × 0 that is equal 0
+ 3594 × 20 which equals 71880
+ 3594 × 400 that is equal 1437600
+ 3594 × 6000 that is equal 21564000

= 23073480
