2+3 is 5, or 2+3 are 5?

2+3 is 5 (2 and 3 are 5)
2+3 ain't 6!
2+3 are now 23 (you may kiss the bride).
2+3 better be 5 (don't bogart a digit)!
2+3 used to be 5 until algebra came along.  Then 2+3=x (where x is 10 (tial))
3+2 ... well, that's a whole other story.

When deciding whether to use is or are, look at whether the noun is plural or singular. If the noun is singular, use is. If it is plural or there is more than one noun, use are. The cat is eating all of his food.

When are numbers nouns? One, two, three, and so on, when used by themselves, are nouns. However, if we use them to describe nouns, as in one apple, two apples, three apples, etc., then the numbers are adjectives.

So, I suppose the correct answer would be: 2 + 3 ARE 5.

Or just forget the rule and say "2 + 3 = 5".

Equals

Depends on whether you're using the old math or the new math.  New math:  2 + 3 = 72.

I have always said 2+3 is 5. In my mind, 2+3 is an equation, a single thing which uses the singular verb. But, this is not something I recall being taught, so it's probably important only to a couple of people. I probably just say it the way people around me say it without thinking about it.