# Carnival of Math No. 173

This year I once again have the pleasure to host the now 173th Carnival of Mathematics, the moveable feast of mathematical blogging shepherded by The Aperiodical, the best math blogging collective on this little blue ball in space. Be sure to visit the previous Carnival (No. 172) at Cassandra Lee Yieng's blog and keep an eye on all Carnivals.

As tradition will have it, we begin our show by taking a closer look at our number.

173 is not just a prime, the sum of two squares of primes (2²+13²) and the sum of three primes (53+59+61). No, it is also a balanced prime (same gap to previous and following prime) and the 13th(!) Sopie Germain prime (since 2×173+1=347 is also prime).

Alas, 173 is also an odious number, which may sound rather bad but just means it has an odd number of 1's in binary (10101101).

Now that you've warmed up, let us once again enter the decidely wonderful, balanced madness of the mathematical blogging carnival.

Likely most people (or at least the most people) will already have seen the NYT's Kenneth Chang looking into Why Mathematicians hate that viral equation; but really who needs 8÷2(2+2) when you can so easily have drama with the Oxford Comma.

In any case, make sure you head over to Over at the Art of Research where Vi Hart shared Computation for Hands, Systems for Humans, taking you on the magic carpet ride that's Vi's hands "craving computation", combining hardware, software, systems thinking, VR and a ton of other ideas.

Before you continue to Ari Rubinsztejn explains Why Tracking Space Debris is so Hard (thanks, nonlinear dynamics!), step under the cover of the Undercover economist Tim Harford who wrote on the strange power of the idea of average, both good and bad.

Of course any mathematically topic is worth a deep dive into, so head into the magical depths of the Math Vault for an extensive article on Long Division and Its Variants (for Integers) Once you're ready, jump out and get yourself back into Cantor's Paradise where Jørgen Veisdal will let you in on the mathematics of Elo ratings, a glimpse at the history of the famous ranking system.

Before you lose your king or queen, let Richard Elwes ask you a question befit Carol's Red Queen: How Many Sides Does A Circle Have? and be sure to follow him off on a tanget or two. If all those tangents twirled you around too much, switch to a classical, sold blog post by the amazing John Cook who will help you estimate vocabulary size with Heaps’ law just in case you need to verify a post-humously discovered manuscript by Jane Austen.

To ease your way out of those particular mazes, take a sip and mingle over at this month's IMA editorial, if only to catch up on the Queen’s Birthday Honours List for 2019. And if you are one of those people who frequent the always dramatic birdsite, here are a two math-focused threads for you:

Also via twitter, Francis Su shared his handout with Guildelines for good mathematical writing (PDF) which he says you should feel free to share with your students.

To wrap things up, take a carousel of math blogging perfection at Math Off The Grid where Benjamin Leis's post on Cardano's Method starts from a new video from Mathologer (below), picks up a tweet by Patrick Honner throws in a podcast with Sam Vandervelde and tops it off with a pointer to Marden's Theorem to drag you into the carnival that is Wikipedia's mathematics articles.

That’s it for the beautiful month of September. Thanks to everyone who submitted a post! After almost 9 years of running

Be sure to stop by next month’s Carnival. You should submit your favorite blog posts/videos/content from the month of September. If you’d like to host an upcoming show, please get in touch with Katie.