Yes. 121 is a palindrome number. Its digits read left to right (1-2-1) are identical to right to left (1-2-1). Other palindrome numbers include 11, 22, 33, 99, 101, 111, 131, 1001, 1221, and 12321.

What are palindrome sentences (also called phrase palindromes)?

Palindrome sentences are phrases that read the same forwards and backwards when spaces and punctuation are ignored. Famous examples include: 'Was it a car or a cat I saw', 'Never odd or even', 'No lemon no melon', 'Do geese see God', 'Step on no pets', and 'Madam I'm Adam'. These are also called phrase palindromes or sentence palindromes.

Are palindromes used in mathematics?

Yes. Palindromic numbers are a well-studied topic in number theory. Every positive integer can be expressed as a sum of three palindromic numbers. The 196 problem (whether repeatedly adding a number to its reverse eventually produces a palindrome) is an unsolved conjecture. Palindromic primes — prime numbers that are also palindromes — include 2, 3, 5, 7, 11, 101, 131, 151, and 181.

Palindrome Checker - Free Online Tool

Check a Word or Sentence

Type or paste any text and click Check . The tool shows whether it is a palindrome, displays the cleaned comparison string, and visualises each character mirror pair.

Enter Text

Ignore case Ignore spaces Ignore punctuation Ignore digits

Try an example:

racecar A man a plan a canal Panama Was it a car or a cat I saw Never odd or even Madam 12321 hello No lemon no melon Step on no pets Do geese see God

Batch Palindrome Checker

Enter multiple words or phrases — one per line — to check all of them at once. The same ignore options from the single checker apply.

One word / phrase per line

What Is a Palindrome?

A palindrome is a word, phrase, number, or sequence of characters that reads the same forwards and backwards. The term comes from the Greek palindromos (πάλιν δρόμος), meaning "running back again" — from palin (again) + dromos (running). Palindromes appear across all human languages and throughout mathematics, literature, and computer science.

Word palindromes: Single words that read identically backwards. Examples: racecar, level, radar, madam, civic, kayak, rotator, deified, noon, refer .

Sentence palindromes: Phrases that are palindromic when spaces and punctuation are ignored. Example: "A man, a plan, a canal: Panama" → cleaned:


        amanaplanacanalpanama

.

Numeric palindromes: Integers whose digit sequence reads the same in reverse. Examples: 11, 121, 1331, 12321, 1234321. Palindromic primes: 2, 3, 5, 7, 11, 101, 131.

Comprehensive List of Palindrome Examples

A categorised reference of the most well-known palindromes in English. Click any row in the single checker above to test it instantly.

🔤 Short Word Palindromes

aba 3 letters
aga 3 letters
bib 3 letters
bob 3 letters
dad 3 letters
did 3 letters
dud 3 letters
eke 3 letters
ere 3 letters
eve 3 letters
ewe 3 letters
eye 3 letters
gag 3 letters
gig 3 letters
mom 3 letters
nan 3 letters
noon 4 letters
peep 4 letters
pep 3 letters
pip 3 letters
pop 3 letters
pup 3 letters
toot 4 letters
tut 3 letters

📚 Common Word Palindromes

civic 5 letters
deified 7 letters
kayak 5 letters
level 5 letters
madam 5 letters
minim 5 letters
radar 5 letters
racecar 7 letters
refer 5 letters
repaper 7 letters
reviver 7 letters
rotator 7 letters
rotor 5 letters
sagas 5 letters
sexes 5 letters
solos 5 letters
stats 5 letters
stets 5 letters
tenet 5 letters

💬 Famous Sentence Palindromes

A man a plan a canal Panama
Was it a car or a cat I saw
Never odd or even
No lemon no melon
Step on no pets
Do geese see God
Madam I'm Adam
Able was I ere I saw Elba
A Toyota's a Toyota
Rise to vote sir
Too hot to hoot
Race fast safe car
Draw, o coward
Murder for a jar of red rum
May a moody baby doom a yam

🔢 Numeric Palindromes

0 trivial
1 trivial
11 2 digits
22, 33 … 99 2 digits
101, 111, 121 3 digits
131, 141, 151 3 digits
1001, 1111, 1221 4 digits
12321 5 digits
123454321 9 digits
1234567654321 13 digits

🔢 Palindromic Primes

2, 3, 5, 7
11, 101, 131, 151
181, 191, 313, 353
373, 383, 727, 757

👤 Palindromic Names

Hannah
Anna
Bob
Eve
Ava
Ede
Elle
Nan
Ono (Yoko)
Lon Nol Cambodia PM

🌍 Longest Known Palindromes

tattarrattat Joyce, 12 letters
kinnikinnik 11 letters
detartrated 11 letters
rotavator 9 letters
Malayalam 9 letters, language
redivider 9 letters
reviviver 9 letters

How Does the Palindrome Checker Work?

The tool uses the two-pointer algorithm — the most efficient method to test for palindromes. One pointer starts at the leftmost character and one at the rightmost. Both pointers move inward simultaneously, comparing characters at each step. If any pair mismatches, the string is not a palindrome. If they meet in the middle without a mismatch, it is a palindrome.

Before the algorithm runs, the input is cleaned according to your selected options — converting to lowercase (ignore case), removing spaces, stripping punctuation, or removing digits — so the comparison is made on the meaningful characters only.

// Two-pointer palindrome check — O(n) time, O(1) space function isPalindrome (str) { let left = 0 , right = str.length - 1 ; while (left < right) { if (str[left] !== str[right]) { return false ; } left++; right--; } return true ; }

Time complexity: O(n) · Space complexity: O(1) · The character mirror visualization shows each matched pair highlighted green and any mismatched pair in red.

Palindromes in Mathematics, Science, and Culture

Mathematics: Palindromic numbers are integers that equal their own digit reversal. The Lychrel number problem asks whether repeatedly adding a number to its reverse always eventually produces a palindrome — 196 is the smallest unresolved candidate. Palindromic primes include 11, 101, 131, and 10301.

Computer Science: Checking for palindromes is a classic algorithm interview question testing string manipulation, recursion, two-pointer technique, and dynamic programming (for longest palindromic substring). The Manacher algorithm finds all palindromic substrings of a string in O(n) time.

Biology & Chemistry: DNA palindromes are sequences where the complement of the reverse strand reads the same as the original strand. Restriction enzymes (used in genetic engineering and CRISPR) recognise specific palindromic DNA sequences as their cut sites.

Literature: Palindromic writing — composing entire sentences or paragraphs that are palindromic — is a literary art form. The longest palindromic novel is "Satire: Veritas" by David Stephens (58,795 characters). James Joyce coined "tattarrattat" (12 letters) in Ulysses as a knock at the door.

Languages: The word "Malayalam" (a language spoken in Kerala, India) is itself a palindrome. Finnish: "saippuakivikauppias" (soapstone seller, 19 letters) is one of the longest single-word palindromes in any language.

Dates & Times: Palindrome dates occur when the date written numerically reads the same forwards and backwards. For example, 02/02/2020 (02022020) and 12/02/2021 (12022021). These dates are rare and often celebrated by puzzle enthusiasts.

Quick-Reference Palindrome Test Table

Common words and phrases with their palindrome status, cleaned form, and character count — useful for quick lookups and teaching examples.

Word / Phrase	Palindrome?	Cleaned Form	Length	Note
racecar	✅ Yes	racecar	7	Classic single-word example
level	✅ Yes	level	5	Common English word
radar	✅ Yes	radar	5	Also an acronym
madam	✅ Yes	madam	5	"Madam, I'm Adam" is also palindromic
civic	✅ Yes	civic	5	Also a Honda model
deified	✅ Yes	deified	7	Theological vocabulary
hello	❌ No	hello	5	Reversed: olleh
world	❌ No	world	5	Reversed: dlrow
python	❌ No	python	6	Reversed: nohtyp
A man a plan a canal Panama	✅ Yes	amanaplanacanalpanama	21	Most famous sentence palindrome
Was it a car or a cat I saw	✅ Yes	wasitacaroracatisaw	19	Classic phrase
Never odd or even	✅ Yes	neveroddoreven	14	Reads same backwards
Step on no pets	✅ Yes	steponnopets	12	Beloved by animal lovers
121	✅ Yes	121	3	11²
12321	✅ Yes	12321	5	111²
123456789	❌ No	123456789	9	Reversed: 987654321

Frequently Asked Questions

What is a palindrome?

A palindrome is a word, phrase, number, or sequence that reads the same forwards and backwards. The word comes from Greek palindromos , meaning "running back again." Examples range from simple words like racecar and level to elaborate sentences like "A man, a plan, a canal: Panama" .

Is "racecar" a palindrome?

Yes. "racecar" reads r-a-c-e-c-a-r forwards and r-a-c-e-c-a-r backwards — identically. It is one of the most frequently cited palindrome examples in English and is often the first word taught when explaining the concept.

Is "A man a plan a canal Panama" a palindrome?

Yes , when spaces and punctuation are removed and the text is case-insensitive. The cleaned string is


       amanaplanacanalpanama

, which is identical forwards and backwards. The phrase was created by wordplay enthusiast Leigh Mercer and published in 1948.

Is 121 a palindrome?

Yes. 121 is a palindromic number — its digits 1-2-1 read identically in both directions. It is also 11², making it a perfect square palindrome. Other palindromic perfect squares include 4 (2²), 9 (3²), 121 (11²), 484 (22²), and 12321 (111²).

What is the longest palindrome word in English?

The longest commonly accepted palindrome in standard English dictionaries is "tattarrattat" (12 letters), coined by James Joyce in Ulysses to represent a knock at the door. In standard dictionary words, "detartrated" and "kinnikinnik" (both 11 letters) are frequently cited. The word "Malayalam" (9 letters) is palindromic and is the name of a language spoken in Kerala, India.

How do you check if a string is a palindrome algorithmically?

The most efficient approach is the two-pointer technique : place one pointer at the start (


       left = 0

) and one at the end (


       right = length - 1

). Compare the characters at both pointers — if they match, advance both pointers inward. If they do not match, the string is not a palindrome. Continue until the pointers meet or cross. This runs in O(n) time and O(1) extra space .

What are palindromic primes?

A palindromic prime is a number that is both a prime and a palindrome. The first several are: 2, 3, 5, 7, 11, 101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929 . Note that 11 is the only even-digit palindromic prime, since any palindrome with an even number of digits is divisible by 11.

Are palindromes used in biology?

Yes. In molecular biology, a DNA palindrome is a sequence of nucleotides where the complement of the reverse strand reads the same as the forward strand. For example: the sequence GAATTC on one strand has the complement CTTAAG, which reversed is GAATTC — a palindrome. Restriction enzymes recognise these palindromic sequences and cut DNA at those sites, which is fundamental to genetic engineering, cloning, and CRISPR research.

Is "level" a palindrome?

Yes. "level" — l-e-v-e-l — reads identically forwards and backwards. It is a 5-letter palindrome and one of the most common single-word examples used in English palindrome discussions alongside "racecar", "madam", and "radar".