Alright, let's work through 2561 times 8216 step by step
2561 × 8216 = 8216 × (2561)
+ 8216 × 1 resulting in 8216
+ 8216 × 60 producing 492960
+ 8216 × 500 resulting in 4108000
+ 8216 × 2000 giving us 16432000

= 21041176
