Alright, let's work through 1645 times 773 step by step
1645 × 773 = 773 × (1645)
+ 773 × 5 giving us 3865
+ 773 × 40 that is equal 30920
+ 773 × 600 resulting in 463800
+ 773 × 1000 producing 773000

= 1271585
