I was always told that Brazilians only refer to each other with their given names and nicknames (or in some instances, with full names) but never with their last name only, no matter how formal or informal the setting is. A similar phenomenon happens in Iceland, but that because they have patronymics instead of proper surnames. This is most famously seen in Brazilian footballers. Since I noticed that Portuguese ones are more likely to have their surnames printed on their shirts, I wonder if there are differences between the two countries. Do Portuguese people commonly use last names to address to each other formally? Or to talk about politicians, celebrities and so on?