It's unusual for a number to be used as an indirect object, but it can be done. For example, "Give the three of them the answer to question #7." In that sentence, "three" is the indirect object.
Indirect objects are best seen as having the word 'to' omitted. In "He gave him an apple" the direct object is 'an apple' and the indirect object is 'him'. It really means 'to him'. So indirect objects are nouns or pronouns.
Indirect objects answer the questions "to whom?", "for whom?", "to what?", or "for what?" in a sentence.
Only transitive verbs have direct or indirect objects
Noun or pronoun
Dative
Difficult is an adjective, so no, it cannot be an indirect object. Indirect objects are nouns or pronouns that receive the direct object.
Offer
Pronouns in the objective case can function as direct objects, indirect objects, and objects of prepositions in a sentence.
A noun that answers the question "To Whom?" ot "To What?" or "For Whom?" or "For What?"
Yes. Marcy sold Joe and his little brother three pizzas for her fundraiser. Marcy is the subject. Pizza is the direct object, because Marcy is selling the pizza's "directly." Who did she sell them to? Joe and his little brother. Thus, Joe and brother are the indirect objects.
Direct Object if you are on A+LS
True. Indefinite pronouns can function as subjects, predicate nouns, direct objects, indirect objects, objects of a preposition, and appositives, serving to replace specific or unspecific nouns in a sentence.