Alright, let's work through 6638 times 3528 step by step
6638 × 3528 = 3528 × (6638)
+ 3528 × 8 which equals 28224
+ 3528 × 30 which equals 105840
+ 3528 × 600 yielding 2116800
+ 3528 × 6000 that is equal 21168000

= 23418864
