Alright, let's work through 1635 times 6543 step by step
1635 × 6543 = 6543 × (1635)
+ 6543 × 5 that results in 32715
+ 6543 × 30 that is equal 196290
+ 6543 × 600 that is equal 3925800
+ 6543 × 1000 that equals 6543000

= 10697805
