Number Reverser
Flip the digits of a number (12345 → 54321) and check whether it is a palindrome.
Number Reverser
Reverse the digits of any number and analyze palindrome properties
Batch Number Reversal
Reverse multiple numbers at once
Digit reversal basics
Reversal rearranges digits from last to first. Trailing zeros become leading zeros and usually drop as a number (1200 → 21). Digit sum and digital root stay the same, so divisibility by 3 or 9 is preserved; divisibility by 2, 4, 5, or 10 often is not.
A palindrome equals its reverse (121, 1331). Single digits are palindromes by definition. The "reverse and add" process (add a number to its reverse, repeat) often reaches a palindrome; some seeds such as 196 are suspected never to (Lychrel candidates).
How code usually does it
Math loop
while n > 0: take n % 10, build reversed * 10 + digit, n = n / 10
String path
toString → reverse characters → parseInt (watch leading zeros)
Both are O(digits). In-place math uses constant extra space; string reversal allocates a buffer proportional to digit count. Digits also show up in check algorithms and simple teaching demos for arrays and recursion.
Frequently Asked Questions
What about leading zeros after reverse?
As an integer they disappear (1200 → 21). Keep them only if you treat the value as a fixed-width digit string.
Are all single-digit numbers palindromes?
Yes. 0–9 read the same forwards and backwards.
Can negative numbers be reversed?
Usually reverse the digits and keep the sign: -123 → -321.
Do palindromes exist in other bases?
Yes. A number can be palindromic in binary and not in decimal, and vice versa.
How do checksums use reversal?
Some schemes rearrange or weight digits (for example Luhn-style checks). Pure reversal alone is a weak integrity check.
What about huge palindromic primes?
Researchers search for large palindromic primes with specialized software. Records change over time; treat any "largest known" claim as dated.
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