Brought to you by Maths Inspiration, this pencil is printed with the largest left-truncatable prime number: this means it remains prime no matter how much you sharpen the pencil. 

357686312646216567629137 is itself prime, but so is 57686312646216567629137, and 7686312646216567629137, and so on all the way down to 7 which is, of course, also prime.

These pencils come in a pack of 10

Watch James Grime explain more about truncatable prime numbers:

Price =  £10.97