Is the object in "Eighty-six forty-five." a proper noun?

The object in the sentence

"Eighty-six forty-five."

refers to the 45th president of the US, as in Bush 41 vs. Bush 43.

The meaning of the verb eighty-six – eject, bar, reject, discard, cancel (Google) – has been addressed in several answers here (e.g. 1, 2, 3, 4).

Should forty-five be capitalized? Is it a proper noun?

Solution 1:

Two reasons why it should have inital caps. Neither alone is perfect.

"Forty-Five" in this case is essentially a nickname. A nickname would be capitalised. To stick to a related example, "Tricky Dick" always has capitals (on both words, Dick of course always would as it's a name).

Many style guides treat "Figure 45" as a proper noun in writing (I believe CMOS is one of the exceptions). By analogy "President 45" or "President Forty-Five" would be proper, then drop the "President".

As this is rather unusual, writing "eighty-six Forty-Five" draws attention to the proper noun, which is no bad thing.