Jag skriver mitt nummer på blanketten.

Because nummer is an ett-word in Swedish: ett nummer.

Swedish possessives change to match the gender and number of the noun:

• min
  • en-word: min bok
• mitt
  • ett-word: mitt nummer
• mina
  • plural: mina böcker

So mitt nummer is correct because nummer is neuter.

You learn it together with the noun: ett nummer.

That is very important in Swedish, because noun gender affects other words in the sentence, such as:

• the article: ett nummer
• the possessive: mitt nummer
• the definite form: numret

So when learning vocabulary, it is best to memorize nouns with their article, for example ett nummer, not just nummer.

Blanketten is the definite form, meaning the form.

In Swedish, the definite article is usually added to the end of the noun:

• en blankett = a form
• blanketten = the form

So på blanketten means on the form, not just on a form.

Swedish often uses på with things like forms, papers, lists, and surfaces where something is written.

So:

• på blanketten = on the form
• på pappret = on the paper
• på listan = on the list

Even if English sometimes says in the form, Swedish commonly says på blanketten in this kind of context.

Skriver is the present tense of skriva.

• att skriva = to write
• skriver = write / am writing / is writing, depending on context

So Jag skriver mitt nummer på blanketten can correspond to English I write my number on the form or I am writing my number on the form, depending on the situation.

Usually, no. Swedish normally uses the simple present form skriver for both:

• I write
• I am writing

Context tells you which meaning is intended.

If you really want to emphasize that something is happening right now, Swedish can sometimes use expressions like håller på att skriva, but in normal sentences skriver is usually enough.

This is the normal basic word order:

Jag / skriver / mitt nummer / på blanketten
subject / verb / object / place expression

So Swedish is behaving very similarly to English here:

I / write / my number / on the form

Nothing unusual is happening with the word order in this sentence.

In modern Swedish, verbs do not change according to the subject.

So you get:

• jag skriver = I write
• du skriver = you write
• han skriver = he writes
• vi skriver = we write

The form skriver stays the same. That makes Swedish verb conjugation simpler than in many languages.

Yes, very possibly. Nummer can mean number in general, and in everyday contexts mitt nummer often means my phone number.

If you want to be more explicit, you can say:

• mitt telefonnummer = my phone number

But mitt nummer is very natural if the context already makes it clear.

The noun blankett is an en-word, so its singular definite form takes -en:

• en blankett = a form
• blanketten = the form

This is a very common pattern for en-words, although Swedish has several noun patterns, so it is still best to learn them case by case.

A rough pronunciation guide is:

Yah skriv-er mitt NUM-mer paw BLAN-ket-ten

A few useful notes:

• j in jag sounds like English y
• sk in skriver is a normal sk sound here
• mitt has a short vowel and a clear final t
• blanketten has the stress on te: blan-KET-ten

The exact pronunciation varies a little by dialect, but that rough version will help you get started.