yes its a unique number and yes, it will force the cache to be flushed for the element. This also can be used as a session-less token so that each web user instance that has activated the player can be individually tracked, and logged. The random number is generated in java by this file:
https://www.radionomy.com/js/radionomy.api.agentid.js by the fallowing code:
code:
function GetAgentToken() {
return 'xxxxxxxxxxxxxxxxxxxx'.replace(/x/g, function (c) { return ((Math.random() * 16) | 0).toString(16) });
}