A vampire number is a number v that is the product of two numbers x and y such that the following conditions are satisfied:
If these conditions are met, x and y are known as "fangs" of v. For example, 1260 is a vampire number because 1260 = 21*60, so 21 and 60 are the fangs.
Write a function that returns all the pairs of fangs for a given number. The output is a matrix in which each row is a pair; the values in the first row should be in increasing order. If it is not a vampire number, it will return empty arrays.
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