Should arbitrary numbers be stored as strings in a database?

I’m using Google as a login system for my latest project. So, my users table has a column named googleid, which stores Google’s unique user id, which is a number, with a few dozen digits. For example, it might be 105561241212957286025. Since I’m not going to do any mathematical operations on this data, should I store it as a number, or as a string, in my database? Also note that if I used a numerical value I would actually have to specify a custom precision because the built-in numerical types in PostgreSQL aren’t big enough for this value.