It represents their chronological position in capped England/Australia players.
E.G Trott is the 626th player to play for England.
The numbers on cricket shirts refers to player numbers. This is similar to the jersey numbers assigned to the tee shirts of football players. It is used to identify the player who is wearing the tee shirt.
In an official match they have to have numbers, so that players can be identified. If players are just practicing or fans are buying shirts, then they don't have to have them.
Blue is the color of the shirts worn by Italian soccer players. That is why they are known as Gli Azzurri("The Blues").
Yes you can create players
The NBA refs do have numbers on the shirts for identification purposes so that all the calls that they make can be documented.
At professional level, many players exchange shirts as a mark of respect for the other player and to show their admiration for the other's skill.
To stand out from the players
4 players were from the RSA. They were Strauss, Pietersen, Prior, & Trott
Those probably are inactive players wearing Super Bowl shirts.
To remember the match - as an item of memorabilia
number of games
These numbers; found on the cap, shirts and jumpers of the players, shows how many players have played for England including himself, when they make their debut. For example, if Ian Bell had number 600 (if he does, it was a good guess), then it would mean he was the 600th different player to play for England.
They play Cricket, mainly, "England vs. Australia".
They were going to the shirt room to cleaning it
The players' numbers mean nothing except to the players. The players get to choose which number they want to wear.
It is belongs to the player. It is about his rank.