Composite Number Checker
Determine whether a number is composite and show its smallest factor.
About Composite Number Checker
A composite number is a positive integer greater than 1 that has at least one positive divisor other than 1 and itself. In other words, it is not prime. The number 1 is special: it is defined as neither prime nor composite. Every composite number can be expressed as a product of primes (the Fundamental Theorem of Arithmetic).
Formula
Composite definition
n is composite if there exists d where 1 < d < n and d | n
- n
- Number to test
- d
- Divisor
Worked example
With the default values below, Composite Number Checker returns Is Composite? of Yes. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Numberminimum 1
- 91
Results
- Is Composite?
- Yes
- Smallest Prime Factor
- 7
- Factor Pair
- 7 × 13
Step by step
- 1Found divisor
- 2Conclusion= 91 is composite
Assumptions and limits
- The result is derived only from the single input listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Is 1 composite?
No. By mathematical convention, 1 is neither prime nor composite. The classification starts at 2.
What is the difference between prime and composite?
A prime has exactly two distinct positive divisors (1 and itself). A composite has more than two — meaning it can be divided evenly by at least one number other than 1 and itself.