sechsmal
six times
Indicates that an action is repeated or that a quantity is present in the number of six.
Ich habe die Prüfung sechsmal wiederholen müssen, bis ich sie bestanden habe.
I had to retake the exam six times before I passed it.

six times
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six times
Indicates that an action is repeated or that a quantity is present in the number of six.
Ich habe die Prüfung sechsmal wiederholen müssen, bis ich sie bestanden habe.
I had to retake the exam six times before I passed it.

The word is a compound of the number 'sechs' (six) and the noun 'das Mal' (time). This structure is used for all number words to express repetition, e.g. zweimal (twice), dreimal (three times), zehnmal (ten times).
Ich habe dich heute schon viermal angerufen.
I have already called you four times today.
As an adverb, 'sechsmal' (six times) can stand flexibly in the sentence. It often stands at the beginning for emphasis (position 1) or in the middle field after the conjugated verb.
Sechsmal habe ich es probiert, aber es hat nicht geklappt.
Six times I tried it, but it didn't work.
When the frequency is meant as a whole, 'sechsmal' (six times) is written as one word. If you want to emphasize the individual events, you can also write 'sechs Mal' separately, with 'Mal' then capitalized as a noun.
Er hat die Tür sechsmal abgeschlossen.
He locked the door six times.
six
'sechs' and 'sechsmal' look similar, but they have different functions. 'sechs' names the number 6, for example with people, things, times, or even as a school grade. 'sechsmal' says how often something happens or is repeated. So you can have 'sechs Äpfel' (six apples), but you call someone 'sechsmal' (six times). The risk of confusion arises because both contain the same number. Ask yourself: Is it about a quantity or number? Then use 'sechs'. Is it about repetition? Then use 'sechsmal'.

Tom hat sechsmal angerufen, aber niemand ist ans Telefon gegangen.
Tom called six times, but no one answered the phone.
Heute beginnt die Besprechung schon um sechs.
Today the meeting starts as early as six.