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earned this badge 5 times
If a prime number is reversed, and then appended to itself, why is the result always a composite number?
Awarded jan 8 at 17:11
Awarded aug 5 '14 at 5:48
Can you answer my son's fourth-grade homework question: Which numbers are prime, have digits adding to ten and have a three in the tens place?
Awarded sep 8 '13 at 5:00
Awarded jul 23 '13 at 20:33
Awarded apr 28 '11 at 16:45