How do I find out my iPad phone number?

cheers.

I just came across this post, and wanted to point out that the phone number of an iPad is useful, especially in a corporate environment. AT&T bills us by phone number. We pay for lots of phone numbers, and the bill doesn't say which numbers are for iPads. Our accounts payable person needs to know what the phone numbers of the iPads are before she can pay the bill.

I need the iPad phone number to sign into an ATT micro cell as I have poor cell reception so I use a micro cell at my home. Thanks