Right Trunctable Primes

These are strange primes in that, if you successively remove the right-most digit another prime results, BUT even stranger is that if you coninue to do this, every "new [smaller]" number will also be prime. Here's an example:




   3             BTW, there is not a "next longer" one in this sequence since there are no primes between 37967 and 37987.

From ask.com:

There are 15 primes which are both left-truncatable and right-truncatable. They have been called two-sided primes. The complete list:

2, 3, 5, 7, 23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397


freeed freeed
66-70, M
4 Responses Apr 18, 2010

i love the way you can feel a prime number. I had a bunch of numbers i felt were just reeally solid and I just found out they were all primes.

I am ashamed to have to admit I have forgotten my Mathematics,what exactly ARE prime numbers,I guess I could look it up on google however since you have contributed with your story..............:-)

A number is called prime when no other number aside from itself divides it with no remainder. One is not considered a prime number, but 2,3,5,7,11, etc, are.

Brieks07: also unpredictable. These numbers are God's monkey wrench; I mean why CAN'T they be divided evenly? Why shouldn't ALL numbers have factors?

Interesting. =)