Quoting from your comment:
I was looking for something in the context of programming where you can have data types that are compound of other data types. I wanted a word to identify the "indivisible" data types.
It sounds like you're asking for a word to describe types like
char, etc. in most programming languages. The most common term I've heard for those is primitive. Some other languages identify them as "built-in" or "basic," but "primitive" is most likely to be recognized by the majority of developers (across all languages) as a term for what you're talking about.
In other contexts, "primitive" would probably not be used to designate an indivisible object. You'd be more likely to hear "indivisible" itself, "fundamental," or "atomic."