Estimated number of ACL (the full name of this key knee ligament is anterior cruciate ligament) injuries that occur each year in the United States. Women are four to eight times more likely to suffer a torn ACL. The ACL tears more often than any other ligament because of the lack of muscle support for twisting or rotational movements around the joint.

Mariano Rivera, of the New York Yankees, tore an ACL while shagging balls during batting practice before a game against the Kansas City Royals in May.

Average duration of brain freeze (or sphenopalatine ganglioneuralgia), which occurs when a cold food or beverage touches the roof of your mouth, causing the blood vessels to constrict and then immediately begin to dilate. Blood rushes back in to warm your mouth, which causes your head to ache. But not much longer than 20 to 30 seconds.

The average lifespan of a human eyelash.

Average number of human skin cells that flake off per minute. In a year, you’ll shed around 8.8 pounds of skin cells.

Number of years ago that North American Inuits made the oldest known kayaks by stretching animal skins over driftwood to make the small, hollowed-out boats. (By the way, “kayak” is a palindrome.)

Number of presidents who have been photographed wearing flip-flops. The footwear pioneer was Barack Obama.

The longest documented engagement was between Octavio Guillen and Adriana Martinez, who were engaged in Mexico in 1902. After 67 years, in June 1969, the two finally tied the knot: They were 82 years old when they married.

The average per-week allowance for 6- to 8-year-olds. The average rises to $7 for kids 9 to 11 and $16.60 for 12- to 17-year-olds.