Alright, let's work through 5138 times 8251 step by step
5138 × 8251 = 8251 × (5138)
+ 8251 × 8 giving us 66008
+ 8251 × 30 giving us 247530
+ 8251 × 100 yielding 825100
+ 8251 × 5000 yielding 41255000

= 42393638
