Enigma 1604: From primes to squares
7 January 2012
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From New Scientist #2769, 17th July 2010 [link]
Harry has been looking for 5-digit perfect squares that can be read (in any order) as a 1-digit prime and two 2-digit primes. He knows that 1 is not a prime. 31329 (177²) qualifies in two ways, since the primes could be 3, 13, 29 or 31, 3, 29. Harry hasn’t found that example, but he has found three squares that each qualify in one way; they use nine different primes.
What are those three 5-digit squares?