Alright, let's work through 1604 times 8591 step by step
1604 × 8591 = 8591 × (1604)
+ 8591 × 4 that results in 34364
+ 8591 × 00 which equals 0
+ 8591 × 600 that results in 5154600
+ 8591 × 1000 producing 8591000

= 13779964
