Eleven is a prime number, divisible by only one and itself. It's the atomic number of sodium. And it's a numerical palindrome, reading the same backward and forward, noted Andrilli, an associate professor.
Today's Veterans Day observance marks the close of a war, World War I, which ended at the 11th hour of the 11th day of the 11th month.
On 11/11, Route 66 was established. Yasser Arafat died. And Demi Moore was born.
Eleven is the number worn by Phillies shortstop Jimmy Rollins. And by old-time Eagles quarterback Norm Van Brocklin. In football, soccer, and cricket, each team has 11 players on the field.
Eleven is half the name of an iconic American business, 7-Eleven, which described the stores' hours of operation in the days before 24-hour service. The most Academy Awards ever won by a movie? Eleven, a feat accomplished by Ben Hur in 1959, Titanic in 1997, and Return of the King in 2003.
In geometry, Andrilli said, an 11-sided polygon is called an "undecagon" - the shape of the one-dollar coin in Canada, whose people have a particular affinity for 11.
The steeple clocks depicted on the country's paper currency are all set to 11. The bright red maple leaf on the Canadian flag has 11 points.
In this country, the Susan B. Anthony dollar coin is round, but it appears to have 11 sides because of the undecagon inside the rim. The back of the coin shows the first moon landing - by Apollo 11.
A line of 11s has been connected to the Sept. 11 terrorist attacks:
The numbers in the date of 9/11 - 9 plus one plus one - equal 11. After Sept. 11, there are 111 days left in the year. The first plane to hit the World Trade Center twin towers - which side by side looked like an 11 - was Flight 11.
Which proves, according to urban-legend collector and debunker Snopes.com, the human propensity for seeing patterns where none exist. It's just as easy to manipulate dates and numbers to tie the attacks to the numeral 2, the website showed.
The Internet is awash in prophecies and end-time predictions surrounding 11/11/11, and people who subscribe to the "11:11 phenomenon" talk of seeing the numbers everywhere - from the record of an 11-1-1 football team to the 11:11 time on digital clock.
Talk-show host Ellen DeGeneres named her record company Eleveneleven, reportedly because she felt she often came across those digits.
Weirdly, the sum of 1,111 multiplied by 1,111 is 1,234,321, another numerical palindrome.
Andrilli, who teaches math history and supervises student teachers, said that without conducting an experiment, it's impossible to know how often 11:11 appears in our lives.
"My guess is it's such an unusual number that when it occurs, like on 11/11/11, it just jumps out at us," he said. "If you counted all the fives in your life, it would probably be the same thing."
He isn't planning a special 11/11/11 observance. But he's confident that the numerals don't mean the end is near, and that the sun will come up on 11/12/11.
Contact staff writer Jeff Gammage at 215-854-2415, firstname.lastname@example.org, or @JeffGammage on Twitter.