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How to Calculate Prime Checker

What is Prime Checker?

A prime number is a natural number greater than 1 that has exactly two divisors: 1 and itself. Primes are the fundamental building blocks of all integers — every integer greater than 1 is either prime or a product of primes (Fundamental Theorem of Arithmetic).

Step-by-Step Guide

  1. 1Trial division: test divisibility by all integers up to √n
  2. 2If n has a factor, one factor must be ≤ √n
  3. 3Optimisation: only test 2, 3, then numbers of the form 6k±1
  4. 4For large numbers, probabilistic tests like Miller-Rabin are used

Worked Examples

Input
17
Result
PRIME
Not divisible by 2, 3, or √17 ≈ 4.1
Input
91
Result
NOT PRIME
91 = 7 × 13 — looks prime but isn't!
Input
2
Result
PRIME
The only even prime number

Frequently Asked Questions

What is Prime Checker?

A prime number is a natural number greater than 1 that has exactly two divisors: 1 and itself. Primes are the fundamental building blocks of all integers — every integer greater than 1 is either prime or a product of primes (Fundamental Theorem of Arithmetic)

How accurate is the Prime Checker calculator?

The calculator uses the standard published formula for prime checker. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Prime Checker calculator use?

This calculator works with inches. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Prime Checker calculator use?

The calculator applies the standard formula for this type of calculation. See the 'How It Works' steps above for the detailed formula breakdown.

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