The 21st century is 13 years old and there are only seven people on Earth who were alive during the 1800s.
In addition to that lucky group, there are only 53 other people on the planet who qualify as "supercentenarians" -- people at least 110 years old.
Colorado filmmaker Hunter Weeks interviewed six of these very old souls for "Walter: The Movie," in hopes of discovering their secrets.
He learned a lot about himself in the process, mainly that it can be difficult asking a 114-year-old man about his secrets to life.
"It's hard seeing old people," Weeks told The Huffington Post. "You're hanging out with them at the end of their years."
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Weeks noted that only two of the supercentenarians interviewed in the film are still alive: Sister Cecilia Gaudette, 109, an American nun living in Rome, Italy; and Juana Bautista de la Candelaria Rodriguez, a Cuban woman who claims to be 128.
The documentary premieres Oct. 4 at the IFC Center in New York and was inspired by Walter Bruening, who lived to be 114 years, 205 days until his death in April 2011.
Weeks first met Bruening in Great Falls, Mont., while doing a project about the state's oldest resident. He was fascinated to be in the presence of a man who was 10 years old when the 1906 San Francisco earthquake happened.
Weeks hoped to find some secret to long life while making the film, but admits there is no exact formula. Bruening smoked cigars until he was 99 (and only quit because of the cost), while former world's oldest living person Besse Cooper loved fried chicken.
"These are people who dodged a lot of bullets," Weeks said. "It comes down to walking a fine line."
All of the supercentenarians shared one common factor: strong wills.
"That was especially the case with Walter. He wanted things his way," Weeks said. "He was having lunch and I went to film him and he said, 'Leave me alone. I have lunch by myself.'"
But getting historical insights with Bruening -- or anyone else over the age of 110 -- presents its challenges, Weeks said.
"Talking to a really old person can be awkward," Weeks said. "I would ask him a question and he would mishear it and answer the question he thought he heard. Sometimes you feel compelled to finish their sentences."
Weeks also discovered that being the world's oldest person is more of a big deal for the people around the supercentenarians than the record-breaking oldsters themselves.
"It's not like they don't care, but they kind of know they're at the top of the list," he said. "In their own communities, their advanced age gives them more respect."
Some advanced oldsters also hope the honor brings them more money, like Rodriguez, an allegedly 128-year-old woman in Cuba.
"She was excited about [possibly being the oldest person on Earth]," Weeks said. "She thought it might bring more money."
The claim also brings controversy, and close scrutiny from a very active online community called The 110 Club that keeps track of who is a contender and who is a pretender for the title of "World's Oldest Living Person."
The group makes a point of analyzing the claims of alleged supercentenarians like Rodriguez as well as Ethiopian farmer Dhaqabo Ebba, who claims to be 160 years old, and Carmelo Flores Laura of Bolivia, who insists he turned 123 in July.
Atlanta-based gerontologist Robert Young, told Weeks he believes Rodriguez is only 96.
Young recently disputed Laura's claims by pointing out a few basic facts about supercentenarians in general: Few people past the age of 110 can walk on their own without help, like Laura, and the oldest age any man has been documented to live is 116.
"Young gets frustrated when people make fraudulent claims," Weeks said. "He wants to know who the oldest person really is."
The "World's Oldest" categories are among Guinness World Records' most popular, and Weeks said one of the most amusing encounters came from the family of Mary Tankursley, who turned 110 during the making of his film and died shortly thereafter.
"The daughters saw that there was growing interest in their mother as she hit 110 and they wanted to know what they could expect in coming years," Weeks said. "It was almost like she was a rookie."