It's a real tracking number but there is no tracking information for it at present. Possible reason is the sender just gave you a tracking number but hasn't shipped it.
You'd better contact the seller to confirm for the reason.
my package has been 19 days "Cleared and awaiting international departure GUANGZHOU (CN)" they've sent this same update twice my tracking number is LZ539542709CN when will I receive my package and where is it?
It's a real tracking number but there is no tracking information for it at present. Possible reason is the sender just gave you a tracking number but hasn't shipped it.
You'd better contact the seller to confirm for the reason.