Questions & Answers about Peter ruft mich später an.
Why is an at the end?
Because anrufen is a separable-prefix verb. In a main clause, the conjugated part (ruft) goes in second position and the prefix (an) moves to the end.
What does an mean here?
As part of anrufen, an- doesn’t carry its own literal meaning; together with rufen it forms the verb meaning to phone/call someone.
Can I drop an and say Peter ruft mich später?
No. Without an, rufen means to call out/shout to someone. To mean phone, you need the prefix: anrufen.
Why mich and not mir?
Anrufen takes a direct object in the accusative. mich is accusative of ich; mir is dative, which is incorrect here.
Can I say Peter ruft später mich an?
It’s grammatical but sounds marked. Unstressed object pronouns like mich typically come before time adverbs: Peter ruft mich später an is the natural choice.