We are pleased to announce the opening of our sister website, PrimeNumberPencil.com!  There, you can buy the perfect gift for the mathematician in your life, the Prime Number Pencil.

The pencil is imprinted with the 24-digit number 357686312646216567629137, which is a prime number. After you sharpen the pencil, it will have the 23-digit number 57686312646216567629137, which is also a prime number. Eventually, it will have the number 37, and then the number 7. No matter how many times you sharpen the pencil, it will be a prime number.

They come in packages of 3, 5, 7, 11, and 23, and shipping is free!