Such a figure is hard to verify, but a big contingent of the team's huge global following undoubtedly lives in the West African nation.
So many Nigerians, like fellow Manchester United supporters from Europe to Asia, were stunned by Wednesday's announcement that veteran manager Sir Alex Ferguson will retire.
"Club football will never be the same again. There are star coaches, there are superstar coaches, there are megastar coaches, and then there is Alex Ferguson," said Sadiq Abdullateef, 38, a lifelong fan in Nigeria's capital, Abuja.
Ferguson, a 71-year-old Scotsman, steps down later this month after 26 years in charge at the club, during which time he became the most successful manager in English soccer history.
Under Ferguson, the club has become a "global brand", and in a survey published last year it claimed to have 659 million followers worldwide, including the 33 million in Nigeria.
Emotions were high on Wednesday in China, where United says it has a following of 108 million. "I never imagined that he would disappear from my world of football. That kind of feeling of not knowing what to do is really awful, and I am not alone," wrote "Hupu Tristan" on Weibo, China's version of Twitter - who admitted to not even being a Manchester United supporter.
In India, fans hailed Ferguson's showmanship. "Standing on the touchline, chewing gum and yelling at players and referees, he was an added entertainment," Dyutiman Basu, a 19-year-old student in Delhi, said.
THE ONLY SPORT THAT COUNTS
To many Nigerians football is the only sport that counts, and the Premier League is the only one they follow, at the expense even of the domestic game.
Passions about the fortunes of Manchester United and its rivals Chelsea, Arsenal and Liverpool run every bit as high in Nigeria as they do back in Britain. Possibly more so.
Nigerians choose their Premier League team for all sorts of reasons. Many flocked to Arsenal a decade ago when Nigerian international Nwankwo Kanu played for the north London team. Some even decided to support Bolton Wanderers, a northern team with conspicuously less success in modern times, when compatriot Jay-Jay Okchoa played there from 2002-2006.
But most are Manchester United fans out of respect for Ferguson and his success in the English and European games. "He has made the impossible possible during his reign as the coach of Man United," said Samson Belimote, a 20-year-old student living in the southern Nigerian oil region.
Top Premier League matches are great social occasions. Nigerians watch on anything from tiny TVs to giant screens erected in open "Bush Gardens" in the country's cities and villages. Beer flows freely, raising passions and provoking the odd scuffle between rival fans.
Supporters wear their teams' shirts, some authorised by the clubs but most produced by an energetic counterfeiting industry. Such is the following that Nigerian billionaire Mike Adenuga sponsors United through his mobile phone company Globacom.
IN FERGIE WONDERLAND
"Gutted is the word. I'm still in shock," said Dhruv Dua, a fan in Delhi. "All of us knew the day was comi
