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設這個數為x因為數位和是質數,所以個位和十比特上的數必定奇偶互异,因為這個兩位數乘以3之後,得到的數的數位和都仍為質數,所以3x的數位加和必定為3.又因為原數是兩位數,3x必定是3位數才能使得數位加和為3,符合…
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