Alright, let's work through 4138 times 813 step by step
4138 × 813 = 813 × (4138)
+ 813 × 8 that equals 6504
+ 813 × 30 what gives us 24390
+ 813 × 100 that equals 81300
+ 813 × 4000 that is equal 3252000

= 3364194
