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

73939133 is the largest prime for which all the initial segments of the decimal expansion are also prime (7, 73, 739, ...). So even if we stop writing before we finish the number, we have still written a prime! Such primes are called right-truncatable primes.

These pencils come in a pack of 10

Watch James Grime explain more about truncatable prime numbers:

Price =  £10.97