# Check Fibonacci Number

## How to check if a number is Fibonacci

There are multiple ways to determine if a number is a Fibonacci. The simplest way and the worst in terms of speed is to just calculate the Fibonacci numbers. If you don't get the number and receive a greater Fibonacci number this means that your number is not a Fibonacci. A better way is to check if the square root of one of these formulas: (5*n2 + 4) or (5*n2 â€“ 4) is a square root. If it is, this means that number is a Fibonacci.

#### Frequently asked questions

- What is a Fibonacci number?

It is a number part of the Fibonacci Sequence. A Fibonacci series is where a number is equal to the previous two numbers sum. - There is a maximum number that can be checked?

Yes, the maximum number is 18446744073709551615