I WAS recently filling in a passport application for my family and in writing down a particular year of birth for one of them I included an extra digit in error. The passport officer rejected the form but the quick-witted clerk noted that the five-figure 鈥測ear鈥� which I had written was a palindromic prime. Interestingly, the same was true if the form was read upside down.
What year had I intended to write?
A 拢10 book token will be awarded to the sender of the first correct answer opened on Thursday 16 February. The Editor鈥檚 decision is final. Please send entries to Enigma 799, New 杏吧原创, King鈥檚 Reach Tower, Stamford Street, London SE99 0BB. The winner of Enigma 799 was Trevor Monk of Chepstow, Gwent.
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Answer to Enigma 799
Going to great lengths
20 metres.