Alright, let's work through 6387 times 3405 step by step
6387 × 3405 = 3405 × (6387)
+ 3405 × 7 what gives us 23835
+ 3405 × 80 that equals 272400
+ 3405 × 300 that equals 1021500
+ 3405 × 6000 giving us 20430000

= 21747735
