There were nineteen items in the list (to which I might add, you might be a mathematician if you count how many items are in long lists).. Here are a few of them, and some reflections.

You might be a mathematician if...

... you have constructed a regular 17-gon with straight-edge and compass (not guilty, but I have done a regular pentagon)

... you videotaped NOVA's presentation of Fermat's Last Theorem and watched it more than once.... (GUILTY.. I even have shown it to my classes... and worse, I also showed them Fermat's Last Tango)

... you've ever tried to prove Fermat's Last Theorem (guilty, repeatedly... dreamed I had the solution and woke up to find.... oooppps, what was that elegant last step)

.... you have ever spent more than two days working on the same problem (guilty, repeatedly, but I'm pretty slow)

... You know whether your birthdate (mmddyy) is a prime (Guilty, and I even know the prime factorization, 2

^{2}x17x1483; Ok, the truth is, I even did that with the mmddyyyy to get 2

^{3}x 3

^{2}x 31 x 4517.... but I am not a complete nerd, I never did it the British way ddmmyy...

... you have ever extracted a cube root by paper and pencil..(guilty, but I didn't really enjoy it... well, only a little)

.... you can't tell the difference between a doughnut and a coffee cup...(actually I can, and I know what kind of coffee cup the joke refers to ... see my blog here ...

....you know who Paul Erdos was...(to which I add, you know how to pronounce it... substitute Euler for the same test.. and my ex-students all know I just crossed myself)

.... YOu know the prime factorization of your social security number (not guilty when I first read it, but then couldn't resist factoring it out, won't give the whole thing, but it does have a seven digit prime... which is pretty cool)

.... you've ever picked Pi when asked to pick a number between one and ten (guilty, so often that now my students are more likely to guess pi or e than they are an integer)

..... you ever tried to calculate the number of blades of grass in your lawn.(too easy, my brown grass is so sparse it is easy to count, but I did estimate the number of grains of salt in a pound of salt [off by about 5%])

...you've ever looked at a word problem and said, "Cool!" (not for a problem, but I have seen some solutions that made me say that, and more... Joshua Zucker's proof of the 25 stones problem is an example)

There were a couple of others, but some additional ones that seem to be appropirate :

... you try to mentally facto license plate numbers, or the time on a digital clock.

....you know how to figure out the day of the week people were born on when you hear their date of birth.

... you can't pass up a list like this without sending in an additional item... so go ahead, send it... if you are mathematician enough....