numeral
fifty
A1
Fünfzig means 'fifty', the cardinal number 50. It’s used as a numeral and attributive modifier (e.g., fünfzig Euro) and is invariant as a numeral but takes normal adjective endings when used attributively. No special preposition or auxiliary; just a basic cardinal number.
Examples
Die Geburtstagsparty ist für fünfzig Gäste geplant.
The birthday party is planned for fifty guests.
Etwa fünfzig Menschen protestierten, obwohl die Behörden die Kundgebung verboten hatten.
About fifty people protested even though the authorities had banned the demonstration.
Details
Mnemonics
Imagine the number 50 on a birthday cake with five tens stacked as candles
fünf + zig (ten-multiple) — remember five-ten groups