Alright, let's work through 8607 times 8121 step by step
8607 × 8121 = 8121 × (8607)
+ 8121 × 7 producing 56847
+ 8121 × 00 giving us 0
+ 8121 × 600 yielding 4872600
+ 8121 × 8000 that equals 64968000

= 69897447
