"Michael has a preference for odd numbers," a team spokeswoman said on Wednesday. "He asked if he could be the odd number and we were happy to accept."
She said the governing International Automobile Federation (FIA) had approved the switch, with Schumacher now having number three on his car and Rosberg four.
As a seven times world champion, Schumacher has spent much of his record-breaking Formula One career with number one on his car. He won all his titles with odd numbers -- five as number one and once with three and five -- and retired with 91 wins.
Since 1973, when drivers were given numbers for the entire season, nobody has started as number four and won the championship.
Odd numbers are not Schumacher's only foible. The German always wore a ceramic amulet, given to him by his wife and with the initials of his family members, when racing for Ferrari.
In 2004, he left it in his hotel in Bahrain and a team member had to rush and collect it before the race, which Schumacher then won. The German said later that the amulet had made "perhaps the decisive difference".