Fibonacci Number Checker
Check whether a nonnegative safe integer is a Fibonacci number.
Description
Check whether a nonnegative safe integer is a Fibonacci number.
Check whether a nonnegative safe integer is a Fibonacci number.
When to use Fibonacci Number Checker
Use this tool to test or transform exact integers according to the named number-theory definition, for education, validation, or algorithm checks.
- Integer
- An integer input greater than or equal to 0.
How the calculation works
The formula below determines the tool output. Is a Fibonacci number: Whether is a fibonacci number is true.1
n is Fibonacci when 5n² + 4 or 5n² − 4 is a perfect square Limitations and assumptions
This tool applies an exact integer definition within JavaScript's safe-integer range. It is not an arbitrary-precision factorization or proof system, so do not use rounded measurements or integers beyond the accepted domain as though they were exact.
Alternative or Complementary approaches
Complement a number-property result with its factorization, divisors, digit representation, or a second independent predicate. A true result establishes only the named property and does not imply other properties such as primality.
References
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Fibonacci number — Wikipedia contributors
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