Alright, let's work through 2580 times 6399 step by step
2580 × 6399 = 6399 × (2580)
+ 6399 × 0 that equals 0
+ 6399 × 80 that equals 511920
+ 6399 × 500 producing 3199500
+ 6399 × 2000 that equals 12798000

= 16509420
