Alright, let's work through 3638 times 5451 step by step
3638 × 5451 = 5451 × (3638)
+ 5451 × 8 that equals 43608
+ 5451 × 30 what gives us 163530
+ 5451 × 600 producing 3270600
+ 5451 × 3000 resulting in 16353000

= 19830738
