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PUZZLET 188

Figurate Pentagonals

Figurate Pentagonal numbers are made by successively stacking dots on a single dot to make nested pentagonal figures. A count of dots at each addition gives the series 1, 5, 12, 22, 35, and so on.

Pentagons

Sometimes the pentagonal numbers have unexpected properties. Take the 118th Pentagonal number, 20827. Add it to its own reversal, and you have 93629, a prime number.

Find all 5-digit Figurate Pentagonal numbers which, when added to their own reversal, make a prime number.


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Last Updated: January 17th, 2010.