Does there exist a positive integer which has exactly 9 positive divisors and whose all divisors can be placed in a 3-by-3 table such that the products of the 3 numbers in each row, each column and on each diagonal are all the same?
Solutions — 2
Solution 1
The number has positive divisors , , , , , , , , . Let the first row be , , , second row , , , and third row , , . Then the product of each row, column and diagonal is .
Solution 2
For each prime the number has exactly divisors . It is known that the numbers to can be placed as a magic square, with an equal sum of the numbers in each row, column and diagonal. By subtracting from each number, we reduce the sum of each row, column and diagonal by . By replacing in the magic square each number by the respective power we obtain a placement of the divisors of in which each row, column and diagonal has an equal product.
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