Alright, let's work through 6455 times 6621 step by step
6455 × 6621 = 6621 × (6455)
+ 6621 × 5 resulting in 33105
+ 6621 × 50 which equals 331050
+ 6621 × 400 that equals 2648400
+ 6621 × 6000 which equals 39726000

= 42738555
