The College Student
I think it's just a number... however, it does depend if it's legal or not. A 12 year old dating a 20 year old? I don't think so. That's completely different and completely illegal. Age is just a number when you're over the age of 18 and older, because that's when you're legally an adult.
So age is not just a number until a person turns 18 at which case age magically becomes just a number?
So what if in another country adulthood is at age 16 or 14?
And what if two people who are 16 and 14 frequently travel between these 3 countries? That would mean that sometimes their age is just a number, and sometimes it isn't.
Furthermore the key thing to notice here is that if you're basing your claim off of laws in a specific country, that means you determine whether age is "just a number" or not depending on the geographic area in which a person is located in. Meaning the actual characteristics of the person no longer are a relevant variable in determining whether they are an adult.
Point being I don't think your opinion is even coherent, because it is not even about analyzing the actual characteristics of the individual person and comparing them to some abstract criteria of what you think an adult is. Rather you are just accepting some arbitrary law that changes depending on which location the person finds them in therefore the entire concept of "adult" becomes nothing about the who the person is but rather it's all about where the person is.
Also "age is just a number" no it isn't, age is not just integer that we assign to people that is abstract/arbitrary. Age correlates very highly with real empirical traits people have that we can measure. Age isn't just a number at all, it's actually a symbolic representation of concrete and real non arbitrary things about a person.
And this fact does not magically disappear once you become a legal adult, age is still more than a number even when you are an adult.