function getID(value) {
    returnvalue = value.split(/;#/)[0];
    return returnvalue;
}
var text =  '1;#Athene';
var abc = getID(text);
console.log(abc);

Simple splitting of a string, just change [0] to [1] if you want to get the text after the ";#" you can change that too.

Split text with jQuery

jQuery