The term you’re looking for is indivisible.
Indivisible refers to something that cannot be separated or divided into parts. It is often used in mathematics to describe numbers that cannot be evenly divided by any other integer besides themselves and one. For example, a prime number is considered indivisible because it has no positive divisors other than one and itself. In a broader context, indivisible can refer to concepts or things that remain whole and intact, emphasizing their integral nature.