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Exercise 1174Algebra › Rings and fieldsL1Added 3 Nov 2026

Prime ideals in $\mathbb{Z}$

#prime ideals#Z#primes

Statement

Determine the prime and maximal ideals of Z\mathbb{Z}.

Hint

nZn\mathbb{Z} is prime iff nn is prime (or 00). nZn\mathbb{Z} is maximal iff nn is prime.

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Solution

Prime ideals. nZn\mathbb{Z} is prime iff Z/nZ\mathbb{Z}/n\mathbb{Z} is an integral domain, iff nn is prime or n=0n=0 (since Z/0Z≅Z\mathbb{Z}/0\mathbb{Z}\cong\mathbb{Z} is an integral domain).

Maximal ideals. nZn\mathbb{Z} is maximal iff Z/nZ\mathbb{Z}/n\mathbb{Z} is a field, iff nn is prime.

Conclusion.
- Prime ideals: (0)(0) and (p)(p) for pp prime.
- Maximal ideals: (p)(p) for pp prime (not (0)(0), since Z\mathbb{Z} is not a field).