Now the sons of Reuben, Israel's firstborn, their genealogical registration by their families, by their fathers' households, according to the number of names, head by head, every male from twenty years old and upward, whoever was able to go out to war,
(New American Standard Bible)
And the children of Reuben, Israel's eldest son, by their generations, after their families, by the house of their fathers, according to the number of the names, by their polls, every male from twenty years old and upward, all that were able to go forth to war;
(King James Version)