123
This number is a composite.
123 x 2123 - 1 is prime. [Noll]
The number formed by the concatenation of odd numbers from 123 down to 1 is prime. [Patterson]
12342 - 1232 - 456 is prime! [Leal]
(There are 2 curios for this number that have not yet been approved by an editor.)
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