Primitive Root Modulo N Calculator

Check primitive roots modulo n with factor tests. Review residues, orders, powers, and generator lists. Download clean reports for lessons, proofs, and homework tasks.

Calculator

Formula Used

A number g is a primitive root modulo n when gcd(g, n) = 1 and ordn(g) = phi(n).

The fast test uses the prime factors q of phi(n). If gphi(n)/q is not congruent to 1 modulo n for every such q, then g is a primitive root.

Euler phi is found from the factorization n = p1a1 p2a2 ... . Then phi(n) = n × product over p dividing n of (1 - 1/p).

How to Use This Calculator

  1. Enter the modulus n.
  2. Enter the candidate g you want to test.
  3. Select candidate testing or range listing.
  4. Enter a search range when listing roots.
  5. Choose how many generated powers to display.
  6. Press Calculate, then review the result above the form.
  7. Use CSV or PDF to save the same calculation.

Example Data Table

n g phi(n) Order Result
1731616Primitive root
9266Primitive root
8342Not a primitive root
14366Primitive root

Understanding Primitive Roots

A primitive root modulo n is a special generator. Its repeated powers create every invertible residue modulo n. This idea is central in elementary number theory. It also appears in cryptography, cyclic groups, and modular arithmetic exercises.

Why This Calculator Helps

Manual testing can become slow. You must find Euler’s totient, factor it, and test power conditions. This calculator performs those checks in one place. It also explains the candidate order and shows residues generated by powers.

What The Result Means

When a number g is a primitive root, its multiplicative order equals phi of n. That means no smaller positive exponent sends g back to one. If the order is smaller, g only generates a subgroup. The result table shows that difference clearly.

Advanced Options

You can test one candidate or list all primitive roots. You can also limit the search range. This is helpful when n is large. The calculator factors phi of n first. Then it checks key exponents from the prime factors. This method avoids unnecessary residue lists.

Learning Value

The power list helps students see cycles. It shows how residues repeat after the order is reached. The missing residue list also explains failure cases. These details make the tool useful for proofs, homework, and lesson preparation.

Practical Notes

Primitive roots do not exist for every modulus. They exist for 2, 4, odd prime powers, and twice odd prime powers. The calculator still tests the actual order. So the final answer remains based on direct modular checks.

Good Input Habits

Use positive integers. Choose a candidate that is coprime to n. Keep the search range reasonable. Very large inputs may take longer, especially when listing every primitive root. Export results after checking them, so your records match the exact inputs used.

How To Read Exports

The CSV file suits spreadsheets. The PDF file suits quick sharing. Both include the modulus, candidate, totient, factors, order, and final decision. When all roots are requested, the list appears too. Use these exports to compare different moduli. They also help document repeatable classroom examples.

Small examples are best for practice. Larger examples help after the method feels clear. Always check coprime status before trusting a candidate test.

FAQs

What is a primitive root modulo n?

It is a number whose powers generate every invertible residue modulo n. Its multiplicative order equals phi(n).

Does every modulus have a primitive root?

No. Primitive roots exist only for 2, 4, odd prime powers, and twice odd prime powers.

Why must gcd(g, n) equal 1?

Only coprime residues are invertible modulo n. A primitive root must generate the invertible residue group.

What is multiplicative order?

It is the smallest positive exponent k where g raised to k is congruent to 1 modulo n.

Why factor phi(n)?

The factorization helps test primitive roots quickly. It reduces the number of modular power checks needed.

Can this list all primitive roots?

Yes. Select the listing mode and enter a range. The tool checks each coprime value in that range.

What does a missing residue mean?

It means the candidate does not generate that invertible residue. Such a candidate is not a primitive root.

Why are large searches capped?

Range listing can be expensive. The cap keeps the page responsive and avoids excessive server work.

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