die Anzahl
number
The amount of things or people that can be counted; a quantity.
Die Anzahl der Bewerber für die Stelle war überraschend hoch.
The number of applicants for the position was surprisingly high.

number
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number
The amount of things or people that can be counted; a quantity.
Die Anzahl der Bewerber für die Stelle war überraschend hoch.
The number of applicants for the position was surprisingly high.

After 'Anzahl' (number), the genitive plural usually follows ('die Anzahl der Bücher' — the number of books). Alternatively, especially in spoken language, 'von' + dative ('die Anzahl von Büchern') or 'an' + dative ('die Anzahl an Büchern') is also used.
Die Anzahl der Bewerbungen hat uns überrascht.
The number of applications surprised us.
Even if the noun after 'Anzahl' (number) is plural, the verb in the sentence agrees with 'die Anzahl' and is therefore singular. It is 'Die Anzahl der Gäste ist…' (The number of guests is…), not 'sind…' (are…).
Die Anzahl der verkauften Tickets ist in diesem Jahr deutlich gestiegen.
The number of tickets sold has increased significantly this year.
'Anzahl' (number) is often combined with adjectives that describe an amount. Common combinations are 'eine große/hohe Anzahl' (a large/high number), 'eine geringe/kleine Anzahl' (a low/small number), or 'eine steigende/sinkende Anzahl' (a rising/falling number).
Eine geringe Anzahl an Fehlern ist akzeptabel.
A small number of errors is acceptable.
amount / crowd
'die Menge' and 'die Anzahl' can both say how much of something there is. 'die Anzahl' is used especially for things or people that can be counted, for example participants, mistakes, or books. 'die Menge' is more general. It works for countable things, but also for substances such as water, sugar, or sand. Learners often confuse the words because both express a quantity. As a simple guide: with an exact number, 'Anzahl' often sounds appropriate; with a general amount or an amount of a substance, 'Menge' is more likely.

Die Anzahl der Gäste steht erst morgen fest.
The number of guests will only be certain tomorrow.
Für den Kuchen ist die Menge an Zucker zu groß.
The amount of sugar is too large for the cake.