What does the Prime Number Checker do?

Check if a number is prime, find prime factorisation, and list primes up to N. All calculations are performed in your browser using official UK rates and thresholds.

How accurate are the results?

This calculator uses standard mathematical algorithms and provides results accurate to the precision shown. For very large numbers or high-precision requirements, results are rounded to a reasonable number of decimal places.

Can I use this for schoolwork?

Yes. This calculator is suitable for GCSE, A-level and university-level mathematics. It follows standard mathematical conventions used in UK education.

Prime Number Checker

Check if a number is prime, find prime factorisation, and list primes up to N.

Last updated: April 2026 · Source: BBC Bitesize — Prime numbers

Enter a Number

is PRIME

Previous Prime

Next Prime

101

Primes up to 97 (25 found):

2357111317192329313741434753596167717379838997

Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

A prime number is a whole number greater than 1 that has no divisors other than 1 and itself. This calculator checks whether any given number is prime by testing divisibility up to its square root. It also finds the complete prime factorisation of composite numbers.

The calculator can list all primes within a range (e.g. all primes between 1 and 1,000) and find the next prime above or below a given number. Prime factorisation is useful in cryptography, simplifying fractions, and finding the least common multiple (LCM) or greatest common divisor (GCD) of two numbers.

Example: Is 97 prime? Factor 360.

97: test divisors up to √97 ≈ 9.85
97 is not divisible by 2, 3, 5 or 7 — it is prime
360 = 2 × 180 = 2 × 2 × 90 = 2 × 2 × 2 × 45 = 2³ × 3² × 5
Prime factors of 360: 2, 3 and 5

Source: BBC Bitesize — Prime numbers

Frequently Asked Questions

What does the Prime Number Checker do?: Check if a number is prime, find prime factorisation, and list primes up to N. All calculations are performed in your browser using official UK rates and thresholds.
How accurate are the results?: This calculator uses standard mathematical algorithms and provides results accurate to the precision shown. For very large numbers or high-precision requirements, results are rounded to a reasonable number of decimal places.
Can I use this for schoolwork?: Yes. This calculator is suitable for GCSE, A-level and university-level mathematics. It follows standard mathematical conventions used in UK education.