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-The product of all the positive factors of 20 ( including 20) can be written2^x.5^y. Find x+y.
-The number 18 is equal to 2 times the sum of its digits: 1+8=9. 2x9=18. There are 4 two digit numbers that are equal to 4 times the sum of their digitss . Find 3 of those 4.