MADRID — Less than two weeks before Christmas, the line to buy a ticket for Spain's biggest lottery at Doña Manolita, which some consider the country's luckiest ticket vendor, was roughly 100 people long on a chilly Tuesday evening.

Considering the frenzy that builds as the holiday nears, it was a short wait. Would-be players will stand for up to three hours in a line that snakes along back streets and past storefronts, crowding the capital city's holiday-festooned pathways for a chance to win the more than 200-year-old drawing known as "El Gordo" — Spanish for "The Fat One" — because it's the richest lottery in the world.

Tickets have sold for months, not just in famed spots such as Doña Manolita but across the country in lottery shops, online and in bars and businesses, the latter which often offer clients and employees the chance to buy in. This year, the pot totals some 2.31 billion euros ($2.4 billion), with the top individual prize worth 4 million euros before the government's 20% cut.

The drawing takes place at Madrid's Teatro Real on Dec. 22, when it will be broadcast (and webcast) across Spain. The stars are two elaborate circular cages: One holds 100,000 balls that will spit out winners' five-digit numbers, which will be matched with balls from a cage of 1,807 balls that denote the corresponding winnings.

In an hours-long, almost-Wonkaesque process, the results are sung — yes, sung — by students from a high school in Segovia before they're verified by officials.

Seen up close, Doña Manolita isn't much. It's a narrow storefront with a simple blue awning and standing room for about 20. But its reputation for luck is such that it's the only place in Madrid many will buy tickets. On busy days, resellers walk up and down the line: They buy sheets of tickets, then hawk them for a few euros above retail, hoping to snare people unwilling to wait. Many decline to budge.

"I come here every year," said 21-year old Ismael Arrieta as he waited. He was there to buy tickets for himself, but he will buy others later: "With friends, family, and at work — if everyone plays, you are obligated to as well," he said.

Indeed, many Spaniards play because they don't want to be left out when others win, said José Antonio Gómez Yáñez, a sociology professor at Universidad Carlos III de Madrid, in an email. "It's striking that 40% of those who buy Christmas lottery tickets say that they would prefer not to buy them."

Staying out can sting: In 2011, all 215 residents of Sodeto, a village south of the French border, won the big prize — except for Greek filmmaker Costis Mitsotakis, who didn't buy a ticket.

Last winter, according to Spain's state lottery agency, people spent an average of 55.24 euros apiece on El Gordo; residents of the north-central city of Soria spent the most, dealing out 204.39 euros each. First prize went to residents of Andalusian beach town of Roquetas del Mar, who reportedly collected around 640 million euros.

Arrieta has never won, but "tradition" draws him to the lottery each year. (His parents, he says, are less keen.) Around him in line are couples, parents with children, and a group of retired Spanish women embodying the ideal of friends who play together. Why? Also "tradition," they explain.

Miguel Sanchez, 57, who lives outside of Madrid, has played every year for nearly four decades. He visited Doña Manolita on a recent evening in search of specific numbers selected by his wife. (Shops sell particular sets of numbers, so choosy players must also pick their vendors carefully. There are websites that offer help.)

"I'm looking for a special number," he said. "With 6 and 5, so my wife wanted me to buy this number. We looked to see where it was selling in Madrid, and they only sold it here."

A local legend that started with a pilgrimage

The roots of the Doña Manolita shop, currently at its third location at Calle del Carmen No. 22 near Plaza del Sol, reach back to 1904, when 24-year-old Manuela de Palbo began selling tickets at a time when female business owners were uncommon in Spain. (She died in 1951.)

According to shop history that has become local legend, trade started slowly as the store didn't hand out any winning tickets. After three or four years, the proprietress, who was known as Doña Manolita, took matters into her own hands, making a pilgrimage to a cathedral in northern Spain.

"Doña Manolita had bad luck, so she went to Virgin del Pilar [Spanish for "Our Lady of the Pillar"] in Zaragoza to ask for good luck," according to Bosco Castillejo, 30, who works in e-commerce at the shop.

After that visit, according to Castillejo, the shop began regularly selling prizewinners, leading to a growing reputation and more clients. The shop has sold an El Gordo winner, Castillejo said, as well as one for El Niño, a smaller drawing on Jan. 6, cementing its fame.

The State Lottery organization declined to name the country's luckiest shops. Others share fame with Doña Manolita, including Loteria Valdés in Barcelona and La Bruixa d'Or, or "Witch of Gold," in the Catalan Pyrenees town of Sort. (That town's name means "luck" in Catalan.)

And Doña Manolita's current owners — unrelated to Manuela de Palbo, who died without heirs — also declined to detail how many El Gordo tickets they sell. "The owners believe it's bad luck," Castillejo said.

A total of 165 million tickets are for sale this year, according to the lottery agency. Players can buy multiple tickets with the same numbers, or tickets with different numbers; the former increases your share of the winnings attached to a specific number, while the latter widens your shot at the jackpot. Some players try both.

So, you've got a five-digit, multicolored El Gordo ticket, embossed as always with a Nativity scene. Are you really holding the key to 4 million euros? Or just 100? Or nothing? What are your odds?

To get an answer, MarketWatch consulted a mathematician. David Orden, assistant professor of applied mathematics at the University of Alcala, northeast of Madrid, last year produced a video that attempted to explain the probability of winning the jackpot that he recreated this year in English for MarketWatch readers.

The chances of picking a ticket to riches is like finding a specific word in "The Hobbit" or a single drop of blood from an entire body's supply, Orden said in an interview. "People usually don't see 100,000 things together, so it's difficult to visualize how small that is," said Orden, in a telephone interview.

The chance of winning something is 0.001%, 1 in 100,000, the number of balls in the big cage. Since there are a number of smaller prizes in addition to the big one, the likelihood of winning any prize at all is about 15%, according to Orden. (Those odds are vastly higher than those associated with the Powerball grand prize.)

Ahead of the draw, 'It's like all the world is waiting'

Players use all sort of strategies to choose numbers. Some use birthdays, wedding anniversaries, street numbers, personal lucky numbers and selections their families have used for years or generations. Past winners have purchased tickets at the last minute, paying little heed to the numbers themselves.

Some who buy tickets at Doña Manolita hunt for those ending in 13, a number widely thought unlucky. Others seek out numbers ending in 5 or 7, according to Castillejo. (The State Lotteries said no first prize has ever been awarded to a ticket ending in 13, though 5 is comparatively common.)

Many Spaniards will pay 20 euros for a "decimo" — a 10th of a full ticket, which costs 200 euros. Winners share their take with anyone who has the same numbers. "It's too easy to believe," said Orden. "The math there should be more complicated."

Oren, who had never bought a ticket before doing so last year for a television interview in connection with his video, described the main response to his explanation as bemusement. "People were like 'I already knew it was difficult, but I don't mind because this Christmas lottery is a social thing,'" he said.

The State Lotteries have also tugged at heartstrings to boost sales. Last year an advertisement told the animated story of a night worker whose daytime colleagues included him in the lottery when they won. This year's TV spot is about an elderly woman who thinks she's won, getting her town all worked up, that finishes with a twist.

Sanchez, a longtime player, has never won and doesn't expect to this time either — "From the point of view of statistics, you have a better chance of winning in other types of lotteries," he said — but the drawing's pageantry and history keeps him coming back. "'El Gordo' is the only lottery where you they put the numbers in a big ball and the kids sing out the numbers," he said.

And so he, his wife, and the rest of his family will do as millions of Spaniards each winter: Buy tickets and hope. "It's like all the world is waiting," he said, describing the excitement of the draw. "'Where did they win now? They won in Sevilla! The second prize was won in Madrid!'"

(Click to display full-size in gallery)Outside Doña Manolita.

(Click to display full-size in gallery)The line to buy Christmas lottery tickets at Madrid’s Doña Manolita.