What does it mean when someone calls and the caller ID number shows 123456?

Question

What does it mean when someone calls and the caller ID number shows 123456?

Answer 1

Often, that is the caller ID that will display when the caller is using Skype.  I've seen this with Skype calls many times in the past.

If Skype user have SkypeIN, it is now possible to set your SkypeOut caller-ID to show your SkypeIN phone number.  Otherwise, it may show something like: 000123456

Answer 2

...see answers above, I've never heard of that before.

Answer 3

Yes that is Skype.