# Definition:Right-Truncatable Prime

## 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

$\blacksquare$