On social media, the club announced the Swedish number. The last time he was in the club he played with number 11, but this time it was busy.
He has never played with number 21 in club context, but in the 2002 World Cup he actually had it on the blue-yellow jersey.
"I will make San Siro bubble again with joy," Ibrahimovic told the club's own channel earlier today.
SVT Sport will broadcast Zlatan's press conference from Milan at 10 am on Friday.