10
This number is a composite.
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In the year '10 of this (or any) century, a person born in '73 of the previous century will be 37 and a person born in '37 will be 73. This pattern is true of many different years and ages, but this is the only pattern represented by two emirps. [Green]
(There is one curio for this number that has not yet been approved by an editor.)
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