Happy (belated) birthday, Pennsylvania.
Sunday was the 223rd anniversary of the day in 1787 when Pennsylvania was admitted to the union as the second state.
Aziz Inan does, and he doesn't even live here.
He's an electrical engineering professor in Oregon, but he has such an obsession for numbers that he took notice of the Keystone State's big day.
That's because Sunday, 12-12-2010, is also what he calls a "reverse perfect square" date.
That means the reverse of the date, 01022121, equals the square of another number, in this case 1011. That doesn't happen very often.
The next time it will is on Dec. 14, 2030. That date's reverse, 03024121, is the square of 1739. After that, the next reverse square date will be Oct. 20, 2062, the reverse of which is the square of 5101.
In the last century, these reverse square dates occurred four times, and just two times in the 19th century.
Because Sunday's date was also the state's birthday -- Pennsylvania became the second state on Dec. 12, 1787 -- Dr. Inan thought it was kind of cool to make the connection.
He's probably the only person in the country who did.
"I realized, 'This is a special birthday they are going to have,' " he said Friday from the University of Portland, where he teaches. "When I found out, I thought, 'My God, I should call some newspapers in Pennsylvania.' "
Number-crunching is the kind of thing Dr. Inan does in his spare time.
He loves number patterns and puzzles. At the beginning of the year, he appeared in dozens of papers discussing his work on palindrome dates, because Jan. 2, 2010, was one of them. (That's a date that reads the same backward as forward).
He also regularly comes up with math quizzes related to Ben Franklin for a historical newsletter, the "Franklin Gazette," and he recently had some fun noodling around with Bill Gates' 55th birthday in the Seattle Times.
"Some people might think this is a waste of time," he said. "But a lot of people like brain-teasers and puzzles. It's good brain exercise. It's part of education. It keeps people's minds active."
There are other interesting aspects of Pennsylvania's birth date, he says:
• When you write the figure 12122010 without the last zero, the number is also a perfect square, because 1101 x 1101 equals 1212201.
• Pennsylvania's 164th birth date came in 1951. That was also a reverse perfect square date, because the reverse of 12121951 is the square of 3989.
• The state will celebrate its 334th birthday on a palindrome date, 12-12-2121.
What does any of this mean?
"I do it for fun," says Dr. Inan.
Torsten Ove: firstname.lastname@example.org or 412-263-1510.