Alright, let's work through 1600 times 2601 step by step
1600 × 2601 = 2601 × (1600)
+ 2601 × 0 resulting in 0
+ 2601 × 00 that is equal 0
+ 2601 × 600 which equals 1560600
+ 2601 × 1000 which equals 2601000

= 4161600
