Alright, let's work through 5187 times 858 step by step
5187 × 858 = 858 × (5187)
+ 858 × 7 that is equal 6006
+ 858 × 80 that equals 68640
+ 858 × 100 giving us 85800
+ 858 × 5000 that is equal 4290000

= 4450446
