Alright, let's work through 2128 times 1865 step by step
2128 × 1865 = 1865 × (2128)
+ 1865 × 8 resulting in 14920
+ 1865 × 20 that is equal 37300
+ 1865 × 100 yielding 186500
+ 1865 × 2000 that is equal 3730000

= 3968720
