My favorite ancient multiplication method is the Egyptian multiplication (also called Russian peasant method and other names). Column a is halved in each step.

My favorite ancient multiplication method is the Egyptian multiplication (also called Russian peasant method and other names). Column a is halved in each step. Column b is doubled in each step. Column r is the remainder of a after dividing by 2. b.r is product of b and r. Product is the sum of column b.r a b r (=a%2) b.r 19 73 1 73 9 146 1 146 4 292 0 0 2 584 0 0 1 1168 1 1168 --------------------------------------- Sum 1168 + 146 + 73 = 1387 --------------------------------------- Interesting observation: Reading the digits in column r from bottom to top gives (10011) in base 2 which is 19 (the multiplier)! That is why the method works.