Alright, let's work through 2640 times 9645 step by step
2640 × 9645 = 9645 × (2640)
+ 9645 × 0 which equals 0
+ 9645 × 40 what gives us 385800
+ 9645 × 600 which equals 5787000
+ 9645 × 2000 which equals 19290000

= 25462800
