Find out instantly whether a word, phrase or number reads the same forwards and backwards. Ignore case, spaces, punctuation and accents, see exactly where a near-palindrome breaks, find the longest palindrome hidden in a text, and explore palindromic numbers.
Check a number
List palindromic numbers
Reverse and add
Add a number to its reverse until the result is a palindrome (87 → 87 + 78 = 165 → 165 + 561 = 726 → 726 + 627 = 1353 → 1353 + 3531 = 4884).
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How to use the Palindrome Checker
Type or paste a word or sentence in the Check text tab. The answer appears as you type.
Choose what to ignore: upper/lower case, spaces and punctuation, or accents.
If it is not a palindrome, the mismatched letters are highlighted and the longest palindrome inside is shown.
Switch to Find palindromes to search a longer text for its longest palindrome and every palindromic word.
Use Palindromic numbers to check a number, get the next and previous palindrome, list palindromes in a range or play reverse and add.
Step on no pets · Was it a car or a cat I saw? · No lemon, no melon
Numbers
121, 1331, 12321, 9009 (the largest palindrome that is the product of two 2-digit numbers: 91 × 99)
Dates
02/02/2020 and 12/02/2021 (written as 12022021) read the same both ways
How many palindromic numbers are there?
Digits
Count
Smallest – largest
1
10 (including 0)
0 – 9
2
9
11 – 99
3
90
101 – 999
4
90
1001 – 9999
5
900
10001 – 99999
6
900
100001 – 999999
A palindrome is fixed by its first half, so with d digits there are 9 × 10⌈d/2⌉−1 of them: the first digit can be 1–9 and the rest of the first half 0–9. Every palindromic number with an even number of digits is divisible by 11.
Finding the next palindrome
To get the next palindrome after a number, copy its first half onto the second half in mirror order. If that is larger than the number, you are done (12345 → 12321 is smaller, so…). Otherwise add 1 to the first half and mirror again (123 + 1 = 124 → 12421). If the first half is all nines, the answer is 10…01 with one more digit (999 → 1001).
Frequently asked questions
What is a palindrome?
A palindrome is a word, phrase, number or other sequence that reads the same backwards as forwards, such as level, racecar, 12321 or “Never odd or even”. For phrases, spaces, punctuation and capital letters are normally ignored.
How does the palindrome checker work?
It removes whatever you chose to ignore (case, spaces and punctuation, accents), then compares the first character with the last, the second with the second-to-last and so on. If every pair matches, the text is a palindrome; otherwise the first pair that differs is highlighted.
What is the longest palindromic substring?
It is the longest continuous part of a text that is a palindrome. For example, in “banana” it is “anana”. The tool finds it with Manacher's algorithm, which runs in linear time, so even long texts are searched instantly.
What are palindromic numbers?
Numbers whose digits read the same in both directions, such as 7, 44, 121 or 9009. All one-digit numbers are palindromes. There are 9 two-digit, 90 three-digit and 90 four-digit palindromes, and 9 × 10^(k−1) palindromes with 2k−1 or 2k digits.
What is the reverse and add process?
Take a number, add it to its reverse, and repeat until the result is a palindrome. Most numbers get there quickly: 56 + 65 = 121. 89 needs 24 steps. For 196 nobody has ever reached a palindrome; such numbers are called Lychrel number candidates.
Is 0 or a single letter a palindrome?
Yes. Any single character reads the same in both directions, so single letters and the digits 0 to 9 are palindromes.
What are some famous palindrome sentences?
Classics include “A man, a plan, a canal: Panama”, “Was it a car or a cat I saw?”, “Madam, in Eden, I’m Adam”, “Step on no pets” and “Never odd or even”. Press Try an example to test them.