This is the

**23rd Math Teachers at Play Blog Carnival**. An enigma to some, twenty-three is the smallest isolated prime, the only prime whose factorial that has a number of digits equal to the prime itself, and it is the smallest prime whose digits reversed is a power (reverse the digits of 23 and observe that $32 = 2^5$). The number 23 is not a munchausen number, but interestingly $23 = -2^2 + 3^3$. Find out more about the number 23 at Number Gossip.

Not sure what this blog carnival thing is? Confused about how

**Math Teachers at Play**gets along with its sister,

**The Carnival of Mathematics**(see the latest at The Endeavour)? Please see this post by Mike Croucher at Walking Randomly.

*image courtesy of Music of the Primes*

We are in a season of holidays, mathematical and otherwise.

In a romantic vein, Mike Croucher sends us A little mathematics for Valentine's day posted at Walking Randomly.

Keeping with the Valentine theme, Tracy Beach presents You’ll Heart Our New February Valentine’s Math Activity Calendar posted at Math Learning, Fun & Education Blog: Dreambox Learning.

Seven days before v-day was e-day, and there were no shortage of posts about it - some of the best of them were collected by Denise in her post Head's up for e-day at Let's Play Math.

Mark your calendars: 35 days after e-day and 28 days after v-day comes pi-day. Start writing your pi-day posts and submit them to the next

**Math Teachers at Play**.

Some truly playful posts were contributed to this edition...

Melissa Taylor gave us Geometry fun with tangrams posted at Imagination Soup.

Letting us know about a great game for home and school that requires all kinds of problem solving skills, Tom DeRosa posted Pentago Board Game Spins Me Round (Like a Record) at I Want to Teach Forever.

Kendra presents Place Value War posted at Pumpkin Patch, and over at Math with My Kids, we learn how to play with Rep-Tiles.

And our final game comes from Brent Yorgey, who blogged about Divisor nim at The Math Less Traveled.

Tributes to mathematicians are always good to read - and in this edition we have tributes to mathematicians from ancient Greece and Victorian England. First, Marc West presents Ode to Pythagorus posted at Mr Science Show: Where Science Meets Pop Culture. Pat Ballew of Pat's Blog follows up with a tribute to Lewis Carroll, who made Logic into a game.

Ahh, infinity... I used up my favorite quote about infinity a few posts ago.

Guillermo P. Bautista Jr. presents An Intuitive Introduction to Limits posted at Mathematics and Multimedia.

Not providing techniques for instructing tiny students, but rather helpful advice on how to think about the almost unthinkable, Jason Dyer at The Number Warrior posts Five intuitive approaches to teaching the infinitely small

Sometimes our intuition fails us when we are confronted with a simple sounding question, like How about infinity plus one? courtesy of the Republic of Math.

Sue VanHattum's math salons sound wonderful, and she talks about her best yet in Richmond Math Salon and Base Three posted at Math Mama Writes....

Helping homeschoolers is also what is done over at HomeSchool Math Blog, where Maria Miller has posted Algebra problem: airplane's speed in still air.

Host of the previous edition of

**Math Teachers at Play**, John Golden posts More Money at Math Hombre.

On a new math blog that already has many great posts, Whit Ford presents Lost points on a problem? What to do... posted at Learning and Teaching Math.

Technology advice is offered by Ryan, who presents How to make a Histogram on Excel posted at Maths at SBHS.

Twitter has given so much, and now it is helping provide advice to young mathematicians, as Peter Rowlett explains in Reading list for a keen 13 year old mathematician on his blog Travels in a Mathematical World.

Writing about something simple that is becoming more important to know but that many people don't understand, John Cook has posted Universal time — The Endeavour at The Endeavour.

Alen has reviewed two great sites to assist with teaching numberlines in Free Math Numberline Activities posted at Technology In Class.

About.com's math blog has recently featured a post about Brightstorm - a tutoring site whose math content is free.

Excellent assessment advice is presented by Sam J. Shah in his post on Binder Checks. See how this strategy inspired other techniques in Kate Nowak's post, The Situation.

Don't let it be said that math blogs shy from controversy.

Joanne Jacobs blogs about controversial education policies in her post, Algebra for All Flunks the Test.

Read a worthwhile debate over the question of whether or not students should be allowed to fail at Unrequited Expectations and Sweeney Math.

And don't let it be said that there we don't have math-blog celebrities.

Marcus du Sautoy has recently written an article explaining why we all need maths as part of the comprehensive feature Do The Maths in the online edition of The Guardian.

Steven Strogatz is writing an ongoing series of blog posts in the NY Times on mathematics, the first post being From Fish to Infinity.

Thanks to all who submitted or agreed to let me link to their posts (and also those whom I didn't ask, but don't mind seeing their work linked to here). Apologies to those who submitted but were not included - we received a record amount of spam, and some great posts may have been lost in the landslide - please resubmit, or submit a new post to the next edition. Thanks also to the spammers who let me know how much money I could be making with a masters degree in nursing (or accounting, or marketing, etc.).

Finally, a reader of blog carnivals might ask, "Will all of these blog postings eventually produce something approaching high art?" Perhaps mathematics, and the Infinite Monkey Theorem, holds the answer. Pat Ballew helps us towards a solution at Typing Monkeys posted at Pat'sBlog.