I don't have much time here, but here's what I learned about the word "number" in German. There isn't a single word that covers all the meanings. Thank you for coming to my TED talk.

No, I'm not kidding. While English collapses several distinct ideas of "number" into a single word "number" (duh), German is, I would say, more explicit.

You'll see what I meant soon.

die Nummer is a number used as an identifier/label. This is the one we are most familiar with. For example, we have:

• Telefonnummer
• Handynummer
• Zimmernummer, usw.

die Zahl is more of a "mathematical number", for the lack of a better term. This is how we say:

• eine gerade Zahl (an even number)
• eine ungerade Zahl (an odd number)
• eine grosse Zahl (a large number)
• eine negative Zahl (a negative number)
• die Zahl 42 (the number 42), usw.

You get the idea, right? This is more than just a label. It's asking about the mathematical value of the number. This is why you see this being used in many german compound words like Zahlensystem (number system).

die Anzahl is what we use to show the count of something. This is commonly used with the Genitive case in the form: die Anzahl + Genitive. z.B:

Die Anzahl der Studenten beträgt 500 (The number of students amounts to 500).

Btw, you can also use die Anzahl von + Dative, both mean the pretty much the same.

Eine große Anzahl von Indern arbeitet im Dienstleistungssektor.

die Ziffer translates to digit. z.B:

Die Zahl 67 besteht aus zwei Ziffern: 6 und 7. (I'm so sorry)

Then we have die Nummerierung, which is basically "numbering". z.B:

Die Nummerierung der Seiten beginnt bei 1.

Given I've been learning german for a while, this kind of neurotic pedantry does not surprise me anymore. But as always, I'm happy to share the bits I learn with my fellow netizens.