Can a cop ask for your SSN?

My daughter was pulled over last night for looking at her phone at an intersection. She was checking the time since the clock on the car does not work. Cop asked her if she knows about the new law concerning Texting and Driving. Daughter said "yes, but this was at a stop light."

The cop asked for DL and insurance card.
He went back to the patrol car and checked things out for about 3 mins.
He came back and ask for her phone # and SSN#. She gave it to him and he said "OK… You can go."

I told her never give the Phone # or SS# out. She said he didn't write it down and was looking at his Ipad or clipboard during this time.

Is this legal? I think a cop can pretty much ask anything, but my daughter only has to give him the DL and insurance. And does not have to provide anything else.

I started to put 2 and 2 together and think that it was because my daughter was driving through a Hispanic neighborhood. She is not Hispanic, but looks to be one and her last name is not Hispanic. The cop may have gotten suspicious and ask for the SSN# to see if she might be illegal immigrant.

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