Alright, let's work through 6435 times 4139 step by step
6435 × 4139 = 4139 × (6435)
+ 4139 × 5 that equals 20695
+ 4139 × 30 which equals 124170
+ 4139 × 400 giving us 1655600
+ 4139 × 6000 giving us 24834000

= 26634465
