If you have Gmail, if you use Google Docs, you have a Google account. At least yearly, review your settings. If you have time, you might also want to read its terms and services.
Here’s just one line for example: “We may collect device-specific information (such as your hardware model, operating system version, unique device identifiers, and mobile network information including phone number). Google may associate your device identifiers or phone number with your Google Account.”
What they don’t say is why, or what they do with it. Can you guess? Yes, to track you, to build up a more complete profile about you, to better serve ads to you.