Le numéro n'est pas lisible sur la copie.

Because ne becomes n' before a vowel sound. The verb here is est, which begins with a vowel, so ne est pas contracts to n'est pas.

This is very common in French:

• je ne ai pas → je n'ai pas
• il ne est pas → il n'est pas

So n'est pas is just the normal negative form here.

French usually makes a sentence negative with ne ... pas around the verb.

Here:

• est = is
• n'est pas = is not

So:

• Le numéro est lisible = The number is legible/readable
• Le numéro n'est pas lisible = The number is not legible/readable

In everyday spoken French, people often drop ne, but in standard written French you keep both parts:

• written/formal: Le numéro n'est pas lisible
• informal speech: Le numéro est pas lisible

In French, nouns normally need an article or some other determiner. So numéro by itself usually sounds incomplete.

That is why French says:

• Le numéro = the number
• Un numéro = a number
• Ce numéro = this number

Using Le numéro is the normal way to refer to a specific number already understood from context.

Numéro is masculine, which is why it takes le:

• le numéro

If it were feminine, it would take la, but that is not the case here.

You can also see this in other combinations:

• un numéro
• ce numéro
• le numéro

Lisible is an adjective meaning legible, readable, or clear enough to read.

It comes from the idea of being able to be read, not from the past participle of lire.

Compare:

• lu = read / having been read (past participle of lire)
• lisible = readable / legible

So in this sentence, lisible describes the condition of the number: it cannot be read clearly.

Because lisible is agreeing with numéro, which is masculine singular. The masculine singular form is simply lisible.

The adjective would change in other cases:

• masculine singular: lisible
• feminine singular: lisible
• masculine plural: lisibles
• feminine plural: lisibles

So in this sentence:

• Le numéro = masculine singular
• therefore: lisible

One useful point: many French adjectives have the same form in masculine and feminine singular, and lisible is one of them.

Sur la copie literally means on the copy.

In context, copie often means:

• a copy of a document
• a photocopy
• a printed copy
• an exam paper or written paper, depending on context

So sur la copie means the number is not readable on the copy itself.

The preposition sur is the normal word for on in this kind of context.

Yes. Copie can mean several related things depending on context, such as:

• a copy of a document
• a duplicate
• a student’s written paper
• an exam script

So la copie does not always mean exactly the same thing in English. You choose the most natural translation from context.

In this sentence, it most likely means something like:

• the copy
• the photocopy
• the paper
• the document copy

Actually, lisible is not directly placed after the noun in a noun phrase. It comes after the verb être in a very common French structure:

• Le numéro = subject
• est = verb
• lisible = adjective describing the subject

This is just like English:

• The number is readable

So lisible is a predicate adjective, used after être.

Yes, absolutely. That would also be correct.

There is a slight stylistic difference:

• n'est pas lisible = is not readable / is not legible
• est illisible = is illegible

Both are natural. Sometimes illisible can sound a bit stronger or more direct, while n'est pas lisible can sound a little more neutral, but in many contexts they mean almost the same thing.

A careful pronunciation would be approximately:

luh nay-may-roh nay pah lee-zeebl sur lah koh-pee

A few useful points:

• Le is usually a light luh
• numéro has the stress pattern of French, which is more even than English
• n'est sounds like nay
• pas is usually pah
• lisible is pronounced roughly lee-zee-bl, with a very light final l
• copie sounds like koh-pee

Also notice the flow:

• Le numéro n'est pas lisible French is spoken smoothly, with words linked together more than in English.

It is neutral standard French. It sounds perfectly normal in writing and in careful speech.

It would fit well in contexts like:

• administration
• school
• documents
• customer service
• general written communication

It is neither especially formal nor casual. It is just standard, correct French.

The plural would be:

Les numéros ne sont pas lisibles sur la copie.

Changes:

• Le → Les
• numéro → numéros
• n'est pas → ne sont pas
• lisible → lisibles

So everything that needs to agree in the plural changes accordingly.