Local math whiz: 9-9-11 is quite unique

Local math whiz: 9-9-11 is quite unique
Photo courtesy Flickr user rosmary (Creative Commons).

PORTLAND, Ore. - Our local math expert who has a serious passion for numbers and dates is at it again - this time pointing out a unique attribute of Sept. 9, 2011.

Dr. Aziz Inan is an Electrical Engineering professor at the University of Portland and every so often he gives us here at KATU News a call to let us know what his number crunching has revealed.

Back in July, he pointed out that 7-26-11 was an extremely rare date because it equaled the product of three consecutive prime numbers.

And of course, Dr. Inan is the same guy you see in those palindrome pictures.

So what about today? What's the deal with 9-9-11? Well for all of us non-math folks, it's a bit complicated, so Dr. Inan was kind of enough to send the following explainer. See if you can follow along.

Today's full date number 9092011 representing September 9, 2011 has a very special, unique property! If one splits this date as 909 and 2011, the difference of these two numbers yield 1102 which is the reverse of the year number! Isn't this sweet?
 
Another way to think about is the difference between this year's number (2011) and its reverse (1102) corresponds to today's date 909 (September 9)!
 
According to my calculations, there exists only 3 such dates in this century. The other two are August 19, 2021 (since that date is 8192021 and 2021 - 1202 = 819, that is, August 19!) and July 29, 2031 (since that date is 7292031 and 2031 - 1302 = 729, that is, July 29!)
 
Also, today's date is more special than the other 2 dates because it corresponds to the same date in both calendar system (that is month/day/year and day/month/year).
 
After year 2031, there won't be any such date in this century!

A quick additional note, the other 2 dates which are 8192021 and 7292031 are not valid dates any way in the other (day/month/year) calendar system used by most of the world whereas today's date 9092011 is valid in both date formats and corresponds to the same exact day!