Number With Prefix, Java-Style Package Identifier Not Valid?

According to the document, for Android, package name “com._123abc.firstapp” should be valid. But when I building, the tools just told me not.
I am using version 2012.840. Is it a bug? [import]uid: 134810 topic_id: 29654 reply_id: 329654[/import]

It’s not a bug. It’s an Android limitation. Please see the link below for Google’s documentation about package names…
http://developer.android.com/guide/topics/manifest/manifest-element.html#package

The key sentence from that web page is…
“individual package name parts may only start with letters” [import]uid: 32256 topic_id: 29654 reply_id: 119127[/import]