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Fibonacci number tester

World's simplest math tool

Free online Fibonacci number tester. Just enter your number on the left and it will automatically get checked if it's in the Fibonacci sequence. There are no ads, popups or nonsense, just an awesome Fibonacci checker. Enter a number – test its Fibonacci status. Created by mathematicians for mathematicians.
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Fibonacci Checker Options
Show a detailed description of all numbers.
Show only a list of Fibonacci numbers.
Show only those values that are not Fibonacci numbers.
Fibonacci number tester tool What is a fibonacci number tester?
This tool tests if the given number is a Fibonacci number. You can check many values at the same time by writing each integer on a new line. There are three types of checks in the options. The first one makes a complete analysis of all numbers and displays each number's status (if it's a fibo or not a fibo). The second filters out only those integers that are Fibonacci numbers. And the third does opposite of what second does – it filters and displays all values that are not Fibonacci numbers. Mathabulous!
Fibonacci number tester examples Click to use
Random Fibonacci Numbers
In this example we input random values on the left and do a full analysis of them. In the output on the right, you get a description of each number. It shows whether it is a Fibonacci number or not.
35 5 51 7 21 65 58 15 82 8
35 is a not Fibonacci number 5 is a Fibonacci number 51 is a not Fibonacci number 7 is a not Fibonacci number 21 is a Fibonacci number 65 is a not Fibonacci number 58 is a not Fibonacci number 15 is a not Fibonacci number 82 is a not Fibonacci number 8 is a Fibonacci number
Required options
These options will be used automatically if you select this example.
Show a detailed description of all numbers.
A Hundred Integers
In this example we load the first hundred integers for testing and return a list of only those that are Fibonacci numbers. There are only 11 Fibonacci numbers between 1 and 100.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
0 1 2 3 5 8 13 21 34 55 89
Required options
These options will be used automatically if you select this example.
Show only a list of Fibonacci numbers.
Large Fibonacci Numbers
This example shows that the tool can check if arbitrarily large integers are Fibonacci integers. Here we invert the display results and print only those values that are not Fibonacci numbers.
81055900096023504197206408605 50095301248058391139327916261 11825896447871834235346346346 19134702400093278082235234534
11825896447871834235346346346 19134702400093278082235234534
Required options
These options will be used automatically if you select this example.
Show only those values that are not Fibonacci numbers.
Pro tips Master online math tools
You can pass input to this tool via ?input query argument and it will automatically compute output. Here's how to type it in your browser's address bar. Click to try!
https://onlinemathtools.com/test-fibonacci-number?input=35%0A5%0A51%0A7%0A21%0A65%0A58%0A15%0A82%0A8&test-all-numbers=true
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