Problems & Puzzles: Puzzles

Puzzle 1232 3338/12/23

Ikemoto publshed the following Curio:

The next left-truncatable prime day when written in YYYYMMDD format (3338/12/23).

Q. Can you find the next right truncatable prime day, in the same format?

From 2 to 8 of August, 2025, contributions came from Giorgos Kalogeropoulos, Carlos Rivera

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Giorgos wrote:

 There are only 83  Right-truncatable primes ( https://oeis.org/A024770/b024770.txt ) and none of these fits the date format (or any other date format)

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Carlos wrote:

My tricky (not valid, just for fun) choice goes for the 59th right-truncatable prime integer: 233993 (days).

This integer, 233993, taken as days elapsed from the very first usage of the Gregorian Calendar, Oct 15 1582, points out to the day June 10, 2223, according to the following online dates calculator. No other smaller integer prime-right truncatable, points out to a date after 2025.


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