Why 137898?
If you don't know what I am talking about, check out the front page. 8D
So I asked the one source which knows everything, Google, and came to the following possibilities:
1) hex color
Yeah, you know, the ones with the # symbol. So, what do we get here?
#137898 is a shady blue without a special name. So I got a picture instead.

Nice, huh?
2) 2(5H)-Thiophenone
The 137898th molecule in the PubChem database. It looks like this:

Despite looking sexy, this molecule doesn't seem to do anything special though...
3) a minor planet
Discovered on January 7, 2000. It's so minor, it doesn't even have a name or picture.
4) number of a star in Serpens

One of those. 8D
4) September 8, 1378
251st day of the year 1378 in the Gregorian calendar. The day of the week is Tuesday. A person born on this day will be 633 years old today. If that same person saved a Penny every day starting at age 7, then by now that person has accumulated $2,288.96 today.
5) a mathematical joke
The numbers 1 3 7 8 9 8 have the mean 6 and checksum 36.
Now 6² = 36.
Haha.
6) a secret file extension?
Type it into your phone and you'll probably get something like this:
.dptwt
Maybe a special version of .dptw, which is already used by DTP Web Servers without having any special meaning.
7) Commonsky's telephone number
Well, at least if he lives in Sweden.
+46-54-137898 is a LANDLINE phone number located in Karlstad, Sweden.
