Well I must be a VERY bad mom then.
I don't know my own 14 years old child's cell phone number

I just can't seem to memorize it, even though I am usually very good with phone numbers. I have her number programmed into my phone's speed dial, so I never ever dial it. And same with her and my cell phone number: she has to look in her phone to tell you what my cell number is.
And my 7 year old son has no idea of our home phone number. I practice it every day with him, but he just can't seem to remember it. Firstly, he's dyslexic, so he just can't seem to get his brain around it. Besides that: there's two phone lines in our house, mom's cell number, dad's cell number, big sister's cell number. So yeah, it's pretty confusing for little guys even if they aren't dyslexic. It's not like when we were little and there was ONE phone number to know. Now there's a pile of them with cellphones, and they even need to know the area code (in my area, we have to dial the area code always, and starting in a few months, the person across the street might be in a different area code than my house)