Definition:Right-Truncatable Prime

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Definition

A right-truncatable prime is a prime number which remains prime when any number of digits are removed from the right hand end.


Sequence

The sequence of right-truncatable primes begins:

$2, 3, 5, 7, 23, 29, 31, 37, 53, 59, 71, 73, 79, 233, 239, 293, 311, 313, 317, 373, 379, \ldots$


Examples

$73 \, 939 \, 133$ is a Right-Truncatable Prime

\(\ds \) \(\) \(\ds 73 \, 939 \, 133\) is the $4 \, 335 \, 891$st prime
\(\ds \) \(\) \(\ds 7 \, 393 \, 913\) is the $501 \, 582$nd prime
\(\ds \) \(\) \(\ds 739 \, 391\) is the $59 \, 487$th prime
\(\ds \) \(\) \(\ds 73 \, 939\) is the $7296$th prime
\(\ds \) \(\) \(\ds 7393\) is the $939$th prime
\(\ds \) \(\) \(\ds 739\) is the $131$st prime
\(\ds \) \(\) \(\ds 73\) is the $21$st prime
\(\ds \) \(\) \(\ds 7\) is the $4$th prime

$\blacksquare$


Also see


Sources