Check Number Palindrome

A number whose string representation reads the same forwards and backwards. Examples: 121, 12321, 1001, 7337. The definition depends on how you represent the number – this tool makes the choice explicit via the mode selector.

No. The check runs entirely in your browser – a string reverse and a compare. Nothing touches the network.

It strips everything except 0-9 before comparing. That makes -121 → 121 (palindrome) and 12.21 → 1221 (palindrome). Useful when you care about the digit sequence regardless of formatting.

It compares the exact trimmed string. So -121 is NOT a palindrome (the minus sign has no match on the right), and 12.21 IS a palindrome (the decimal point mirrors itself).

Yes. 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 each read the same in both directions – the simplest case of palindromic numbers.

It depends on the mode. In “digits only” mode, negatives can be palindromes because the minus sign is stripped. In “strict” mode, the leading minus has no match on the right end so negatives are never palindromes.

A number whose base-2 (binary) representation is itself a palindrome. For example, 9 in binary is 1001, which is a palindrome. The tool shows this as a bonus stat when the input fits in a safe JavaScript integer.

A number with a single repeated digit (111, 4444, 77777). Every repdigit is a palindrome; the reverse also holds only for length-1 numbers.

A forward/backward linear scan over integers, bounded by a 1,000,000-step limit so very large inputs don’t freeze the tab. The boundary is almost never reached for normal inputs – the longest gap between palindromes up to a million is tens of steps.

After the page loads, yes. HTML, CSS, and JS are self-contained – disconnect Wi-Fi and keep checking.