Sam Loyd's Battle of Hastings Puzzle

The Puzzle:

Sam Loyd's Battle of Hastings Puzzle
In the Battle of Hastings that occurred on October 14, 1066 Harold's forces formed 13 similar squares with exactly same number of soldiers in each square.

When Harold himself joined the fray and was added to the number of his soldiers in those thirteen squares a single huge square could be arranged. How many men there must have been in Harold's force?



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-\./^\./-


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