The number 23 made the headlines for the second time in a week on Wednesday - Beckham's unveiling at Real came days after Manchester City retired their number 23 shirt following the death of Cameroon midfielder Marc-Vivien Foe.
Jordan wore the 23 shirt for the Chicago Bulls.
Beckham will be very familiar with at least one other number 23 in the Spanish first division, Aldo Duscher of Deportivo Coruna.
The Argentine midfielder broke Beckham's foot in a tackle during a Champions League match last year, jeopardising the England captain's participation in the World Cup.
Other 23's in the Primera Liga include Spanish international strikers Raul Tamudo and Jose Mari of Espanyol and Atletico Madrid respectively, and Mexico midfielder Gerardo Torrado of Sevilla.
The premier league's highest profile 23 is England defender Sol Campbell, who took the number when he joined Arsenal from their arch-rivals Tottenham Hotspur two years ago.
Others include Tottenham's German international Christian Ziege, Liverpool's England defender Jamie Carragher and Chelsea's Italian goalkeeper Carlo Cudicini.
Beckham wore the number seven shirt for his former club Manchester United, taking it over from Eric Cantona after the French striker retired in 1997. He always wears seven for England.
Foe collapsed on the field and died of an apparent heart attack shortly after the Confederations Cup semifinal against Colombia last Thursday.
