Palindrome Number
A easy-tier problem at 59% community acceptance, tagged with Math. Reported in interviews at Cognizant and 32 others.
Palindrome Number is an easy math problem that appears deceptively simple but trips up candidates who overthink the approach. Cognizant, Accenture, Infosys, and TCS ask it frequently. The acceptance rate hovers around 59 percent, which means nearly half the candidates who attempt it either time out on edge cases or pick an inefficient solution. The trick isn't complex, but if you blank on it during your live assessment, StealthCoder surfaces the optimal approach instantly while the proctor sees nothing.
Companies that ask "Palindrome Number"
Palindrome Number is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Built by an Amazon engineer who used it to pass JPMorgan's OA and system design loop.
Get StealthCoderThe problem tests whether you can identify that converting to a string is the lazy path and math operations are cleaner. Most candidates either reverse the number mathematically or convert it to a string and compare. The math approach is actually faster and avoids string allocation overhead. The real pitfall is handling negative numbers and the edge case where the number ends in zero, which can't be a palindrome unless it's zero itself. Candidates often waste time on unnecessary checks or miss the mathematical property that lets you reverse half the number and compare without touching strings. StealthCoder covers both approaches and flags the gotchas before you hit submit.
Pattern tags
You know the problem.
Make sure you actually pass it.
Palindrome Number recycles across companies for a reason. It's easy-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Built by an Amazon engineer who used it to pass JPMorgan's OA and system design loop. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Palindrome Number interview FAQ
Is Palindrome Number actually asked in real OAs?+
Yes. Bloomberg, Cognizant, Deloitte, and Roche have all reported asking it. At 33 companies total in the dataset, it's a staple of entry-level and screening rounds. The 59 percent acceptance rate suggests it's used to filter candidates who rush through edge cases.
What's the actual trick to solve it efficiently?+
Reverse the number mathematically by extracting digits via modulo and division, rather than converting to a string. Compare as you build the reverse. The trick is realizing you don't need to reverse the whole number: reverse half and stop when the reversed portion equals or exceeds the remaining number.
What are the edge cases everyone misses?+
Negative numbers are never palindromes. Numbers ending in zero can't be palindromes unless the number is zero itself. Single-digit numbers are always palindromes. Many candidates hardcode palindrome checks for small numbers instead of using one clean logic path.
Does string conversion work, or should I avoid it?+
String conversion is correct but slower and uses extra memory. It's acceptable if you're short on time during the OA, but the math approach is preferred by companies like Cognizant and Infosys that ask this. If you can't recall the math trick live, string reversal is your fallback.
Why do so many people fail this if it's marked easy?+
The problem is algorithmically simple but conceptually fragile. Candidates either overthink the approach, miss one edge case (usually negatives or trailing zeros), or implement inefficiently. The 59 percent acceptance rate reflects rushed solutions that work on happy paths but fail on the OA's test suite.
Want the actual problem statement? View "Palindrome Number" on LeetCode →