Oscar Piastri on why he chose number #81
He explained why he chose the number #81 for his car in his debut season with McLaren

Oscar Piastri explained why he chose the number #81 for his car in his debut season with McLaren.
Oscar Piastri: "When I participated in my first race, I had to choose a number, and there were only "ones" in the nearest store. I couldn't use number 1, so I chose #11.
Then I participated in the go-kart championship in Victoria, where someone has already performed under #11, chose #81, and since then I have used it several times.
In Formula 1, the car with the number 81 last appeared in 1957 in the "500 miles of Indianapolis" race, when it entered the championship standings – it was used by Tony Bonadies, but did not qualify. Before him, the numbers 81 were on Maurice Trintignant's car during the 1951 German Grand Prix at the Nurburgring”.