Holland international Van De Beek, also 23, explained why he had chosen shirt number 34 in an interview on United's official website.

"This is a special thing for me because my good friend Abdelhak Nouri... maybe you know the story, he had a heart attack and he's a good friend of mine.

"I'm really close with his family and his brother is one of my best friends and I talk a lot with them.

"So I decided to take his old number on my shirt and I want to get good memories with this number."

Van De Beek played an important role in Ajax's thrilling run to last year's Champions League semi-finals and has signed a five-year deal at Old Trafford with the option of a further season.

"I cannot begin to explain how incredible an opportunity it is to join a club with such an amazing history," Van De Beek said.

"I would like to thank everyone at Ajax, I grew up there and I will always have a special bond with the club.

"I am now ready to take the next step in my career and perform at the highest level and there is no higher standard than Manchester United.

"Everyone has told me how amazing the Old Trafford atmosphere is and I am looking forward to experiencing that, once it is safe for the fans to return.

"This team has some of the best midfielders in the world and I know that I can learn from them and also bring my own strengths to the group.

"Having spoken to the manager about his vision for this team, the direction that the club is going in is hugely exciting and I cannot wait to be a part of that."

Van De Beek came through the ranks at Ajax and has gone on to establish himself in the Holland national team.

He will head to Manchester after the Oranje's upcoming Nations League double-header with Poland and Italy.

United boss Ole Gunnar Solskjaer said: "Donny has all of the technical attributes needed to perform in this team and has the personality required to succeed at Manchester United.

"His ability to see space, time his movements and read the game will really complement the qualities that we have in midfield and his arrival really strengthens the depth of talent we have in that position.

"Donny's performances in the Eredivisie and in Europe have been excellent over the last few years and we are all looking forward to working with him."

Ajax's director of football affairs Marc Overmars wished Van De Beek all the best at Old Trafford.

"This is a great transfer for Donny, one which he deserves," he said. "It's also a compliment to Ajax's youth academy, where he has played since he was 11.

"Last summer there was a lot of interest in him but, luckily, we were able to keep him at Ajax for one more year.

"In the months that followed, he proved very valuable to us in both domestic and European competitions.

"He has now been a part of the Ajax first team for almost five years. He is ready for this step and we will miss him."