Answer: 3 More information: Octopuses have three hearts; two branchial hearts that pump blood through each of the gills. The third heart is a systemic heart that pumps blood through the whole body.

Answer: Paul Erdős More information: Erdős published at least 1,525 mathematical papers during his lifetime. He engaged more than 500 collaborators and devoted most of his time to mathematics up until his death in 1996 at the age of 83 years old.

Answer: Stork More information: Storks are large birds with long legs, long necks, and long bills. This association came from a German folk tail that said storks found babies in caves or marshes and brought them to households in a basket.

Answer: O- More information: People with O- blood can give blood to anyone. The other blood types can only donate to certain people depending on their blood type. For example, if you are AB+ you can only donate to other AB+ blood types, but you can receive blood from anyone.

Answer: Leonhard Euler. More information: Swiss-born Euler is held to be one of the greatest mathematicians in history. He made pioneering contributions to several branches of mathematics and introduced much of the modern mathematical terminology and notation.

Answer: Femur More information: The Femur is not only the longest bone in the human body, it is also the strongest bone. The Femur bone is located in the thigh.

Answer: Carbon More information: Scientists speculate that diamonds originated from carbon dioxide atoms 100 miles below the Earth's surface more than a billion years ago.

Answer: A perfect number. More information: You might also think of a perfect number as a number that is half the sum of all of its positive divisors, including itself! This definition is at least 2300 years old as it appears in Euclid's "Elements".