# You're reading: Posts Tagged: prime numbers

### Mobile Numbers: Products of Twin Primes

In this series of posts, Katie investigates simple mathematical concepts using the Google Sheets spreadsheet app on her phone. If you have a simple maths trick, pattern or concept you’d like to see illustrated in this series, please get in touch.

Having spoken at the MathsJam annual conference in November 2016 about my previous phone spreadsheet on multiples of nine, I was contacted by a member of the audience with another interesting number fact they’d used a phone spreadsheet to investigate: my use of =MID() to pick out individual digits had inspired them, and I thought I’d share it here in another of these columns (LOL spreadsheet jokes).

### Are you sure 51 isn’t prime? – Analysing the results of the “Is this prime?” game

Two months ago, I bought isthisprime.com and not only set up the internet’s fanciest primality-checking service, but also invented a rather addictive game.

It quite quickly went viral, or as relatively viral as a maths game can get, with people tweeting their high scores and posting the link to reddit and Hacker News. I realised fairly soon that I should put in some stats tracking, to see if there were any interesting patterns in the data (and also to inflate my ego as the “games played” counter went up). I missed the first big spike in traffic, but on the 9th of March I wrote a script which saved a record of each game to a database.

The mad rush settled down quite quickly but there were still occasional spikes as different sites or people with lots of twitter followers found the game. Now, after two months, I’ve got data for just under 350,000 games. That’s a decent amount of information!

### Not mentioned on The Aperiodical, March 2016

There’s been a lot of maths news this month, but we’ve all been too busy to keep up with it. So, in case you missed anything, here’s a summary of the biggest stories this month. We’ve got two new facts about primes, the best way of packing spheres in lots of dimensions, and the ongoing debate about the place of maths in society, as well as the place of society in maths.

### A surprisingly simple pattern in the primes

Kannan Soundararajan and Robert Lemke Oliver have noticed that the last digits of adjacent prime numbers aren’t uniformly distributed – if one prime ends in a 1, for example, the next prime number is less likely to end in a 1 than another odd digit. Top maths journos Evelyn Lamb and Erica Klarreich have both written very accessible pieces about this, in the Nature blog and Quanta magazine, respectively.

Oliver and Soundararajan’s paper on the discovery is titled “Unexpected biases in the distribution of consecutive primes”.

### I bought isthisprime.com

Around about exactly this time a year ago, I bought the frivolous domain name three.onefouronefivenine.com, to celebrate π Day and to indulge my curiosity about a marvellous algorithm to compute π’s digits.

This year, I’ve been thinking about prime numbers, and my hosting provider has run another sale on domain names. So, I’ve bought isthisprime.com. You can probably guess what I’ve made it do.

### New Mersenne prime discovered, and promptly printed out

Breaking news! On 19th January 2016, the Great Internet Mersenne Prime Search discovered a new largest prime number – we know 49 Mersenne primes, the largest of which is now $2^{74207281}-1$, a number containing over 22 million digits and full of primey goodness.

Internet Maths Person Matt Parker has responded to the news in spectacular style, by issuing a 14-minute long video explaining the discovery and its implications, as well as somehow scoring an interview with the actual discoverer of the new prime, Curtis Cooper.

### Things I Made And Did

Since you’re here reading this, you probably know that on October 30th, Matt “Friend of the Site” Parker released his book, Things to Make and Do in the Fourth Dimension. If you’ve gone one further and read it, you might have seen the occasional reference to the website, makeanddo4d.com. If that website is the book’s DVD extras, this is the website’s extras. We’re going to peek behind the scenes and see how it all works. (Spoiler alert: the maths is powered by maths. It’s recursive maths, all the way down.)

### New Mersenne primes not discovered

The Great Internet Mersenne Prime Search, the premier distributed-computing prime finding initiative, has reported that $M_{32582657} = 2^{32,582,657}-1$, the 44th Mersenne prime to be discovered, is also the 44th Mersenne Prime in numerical order. It was found by Steven Boone and Curtis Cooper in 2006 (Cooper also discovered the current largest prime as reported here in February), but until now it was not known for certain that other, smaller primes had not been overlooked. GIMPS has now checked all the intervening Mersenne numbers for primality and having found nothing, $M_{32582657}$ is secure in its 44th-ness.

### Further information

The Great Internet Mersenne Prime Search (announcement on the front page as of November 10)

Their page for the prime itself

Mersenne Prime at Wolfram Mathworld