js超过18位最后转为0是什么情况

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js:

传入：deviceid

function getDeviceMedia(deviceid){

var devicess new String(deviceid);
alert(devicess);//弹出的回是答61040000001315000000
SMNOcx.setScreenNumber(4);
SMNOcx.setSipInfo(0,deviceid,&39;192.168.21.202&39;, 12501);
}