You appear to be assuming mathematical platonism? — Michael

No, I'm not assuming mathematical Platonism or anything else.

The proposition "X is a prime number" is assessed as accurate/true when uttered. — Michael

As I said I'm not proposing anything. I just write down a number and ask the question as to its primeness. I know the truth regarding its primeness is prior to even writing the number down and certainly prior to my discovering it. And of course I will have to discover it, most especially in the case of extremely large numbers.

But "a truth" means "a true proposition", and so you are saying "there is a true proposition about whether or not that number is prime; no proposition required". — Michael

You are simply asserting, without supporting argument, that truth is only a property of some propositions. If you open your mind and think about it you will see that my example of prime numbers throws that assumption into question—makes it look like the partial, not the whole truth.

Also, accuracy is not a precisely d;eterminable quality.
— Janus

Then neither is the truth of the proposition "the painting is accurate — Michael

I agree, but it is irrelevant to the question about prime numbers.

If you open your mind and think about it you will see that my example of prime numbers throws that assumption into question — Janus

You seem to be saying that the proposition "X is a prime number" is true or false before it is uttered but denying that this is a case of a proposition being true or false.

I'll try one last time If you won't address what I actually write, there is no point continuing. I haven't uttered any proposition; I've just nominated some extremely large number and asked the question about its primeness. Do you deny that the truth regarding the number's primness is prior to my proposing anything about it, and in fact prior to my even nominating it, or not. If not, why?

- See this exchange and following:

Just as a sentence being true (or false) before it is said makes no sense. — Michael

What are the chances that anyone has ever said that 799168003115 + 193637359638 = 992805362753? — Srap Tasmaner

Right...a very similar point. And yet @Michael remains oblivious it seems...or willfully blind.

I'll try one last time If you won't address what I actually write, there is no point continuing. I haven't uttered any proposition; I've just nominated some extremely large number and asked the question about its primeness. Do you deny that the truth regarding the number's primness is prior to my proposing anything about it, and in fact prior to my even nominating it, or not. If not, why? — Janus

I went over this with the existence of gold, but I'll do it again with a number being prime:

1. "11 is prime" is true
2. It is true that 11 is prime
3. 11 is prime

(1) asserts that a proposition is true. (3) asserts that a number is prime (and says nothing about truth).

(2) either means the same thing as (1), in which case it asserts that a proposition is true, or it means the same thing as (3), in which case it asserts that a number is prime and the phrase "it is true that" is vacuous, being nothing more than grammatical fluff.

When you ask about the truth regarding a number's primeness it's unclear if you're asking me about the truth of the proposition "X is prime" or if you're asking me about the number's primeness, and this ambiguity is causing you to equivocate.

The unambiguous and correct answers to your question are:

1. If I say that the number 11 is prime then what I say is true
2. The number 11 is prime even if I don't say that it is
3. If I say that the number 12 is prime then what I say is false
4. The number 12 is not prime even if I don't say that it isn't

And to a different question:

1. If I say that gold exists then what I say is true
2. Gold exists even if I don't say that it does
3. If I say that vibranium exists then what I say is false
4. Vibranium does not exist even if I don't say that it doesn't

When you clear up the grammar of the questions and answers then it's clear that truth and falsity are properly properties of propositions/sentences/beliefs/utterances, not something that can be divorced from them by clever word play, and is why the SEP article on truth says:

We thus find the usual candidate truth-bearers linked in a tight circle: interpreted sentences, the propositions they express, the belief speakers might hold towards them, and the acts of assertion they might perform with them are all connected by providing something meaningful. This makes them reasonable bearers of truth.

So the relevant discussion concerns whether or not platonism about truthbearers is correct, or if we should adopt a non-platonistic interpretation that allows for a distinction between truths in a world and truths at a world, and I am firmly in favour of the latter.

So the relevant discussion concerns whether or not platonism about truthbearers is correct, or if we should adopt a non-platonistic interpretation that allows for a distinction between truths in a world and truths at a world, and I am firmly in favour of the latter. — Michael

It seems to me your thinking is too black and white. If there are countless prime numbers which no one will ever identify, then we can write down extremely large numbers and for any number we write down it will be true or false that it is prime, even if we don't know the answer. If the truth about the primeness of those countless numbers precedes their being enunciated, then what is it that determines that truth or falsity. It's a different case than with concrete particulars because the latter can be observed in order to find out whether what we thought about them prior to knowing the answer is true or false.

This is a difficulty for the idea that truth is simply a property of propositions, but it doesn't follow that Platonism is the answer. Maybe the question cannot be answered, but even so that doesn't remove the difficulty..