A semiprime (7 × 13) which John Conway called "the first number that looks prime but isn't". It's easy to tell if a number has a factor of 2, 3, 5, or 11 at a glance, but there's no good shortcut for 7 and 13.
Humanity has always struggled with numbers. We’ve scraped by with our ten fingers for thousands of countless years, but our modern world threatens to turn us all into machines as it forces ever-longer digit sequences into our heads.
Let’s say you need to memorize the six-digit code 325587. Such an act would typically cost a fraction of your soul. But with the right training, you can defensively convert these unnatural numbers back into human-friendly concepts: 32 is freezing point in Fahrenheit (the most humanist temperature scale), 55 is the speed we all pretend to drive on the highway, and 87 is the famous Gettysburg Address number (“Four score and seven years ago...”). Now you’re imagining Abraham Lincoln driving down the highway in the winter, hoping he doesn’t hit a patch of ice. Your soul is safe!
Here at 2digit.org, we’re building a catalog of every two-digit number from 11 to 99 (skipping the pure multiples of 10, at least for now), and we need your help! Certain numbers are more unnatural than others, and may require more creative associations.
Now, let's try another code, this time randomly generated:
Creating a mnemonic is left as an exercise to the reader, with help from the following entries in the catalog: