Can "trusted number" be my own iPhone?

My iPhone is both a trusted device and a trusted phone number but I also have a second trusted phone number. If your phone is the only trusted device and trusted phone number and it is lost, recovery is not simple.

Also see the following from Two-factor authentication for Apple ID - Apple Support

You should also consider verifying an additional phone number you can access, such as a home phone, or a number used by a family member or close friend. You can use this number if you temporarily can't access your primary number or your own devices.

What I use is a Google Voice number as a trusted number, because it can forward to any other phone or phones (simultaneously). And it can also handle SMS directly.

My memory is probably wrong but I think it defaulted my phone to being a trusted phone number (as well as a trusted device). I do know that it will allow the phone to be the one and only trusted phone number, which is something I don't think it should allow.

by default it uses the number associated with the device for the trusted number and Lawrence is correct. You need to have a additional trusted number because if you lose access to the original and don't have a additional trusted number there is no way to receive verification codes. ALWAYS HAVE TWO TRUSTED NUMBERS VERIFIED ON YOUR ACCOUNT

Your iPhone is a trusted device. Trusted numbers are non-Apple numbers like your home or office number or a friends Android phone.

FoxFifth wrote:

My iPhone is both a trusted device and a trusted phone number but I also have a second trusted phone number.

It never occurred to me you could do that. Good to know.

I've never tried to use it as a trusted number. I've only every used my work phone for that.