Curated
24| # | Title | Difficulty | Source | Tags | |
|---|---|---|---|---|---|
| 13 | Squares leave a traceDivisibility | Easy | Lemma | ||
| 24 | The nine testDivisibility | Easy | Lemma | ||
| 36 | Every square is a sum of oddsOdd numbers | Easy | Lemma | ||
| 567 | A greatest common divisorDivisibility | Easy | Lemma | ||
| 568 | A least common multipleDivisibility | Easy | Lemma | ||
| 570 | A remainderDivisibility | Easy | Lemma | ||
| 571 | Odd divisorsDivisibility | Easy | Lemma | ||
| 572 | Factor 1001Divisibility | Easy | Lemma | ||
| 1125 | Divisibility by eight via last three digitsDivisibility | Easy | Hall & Knight | ||
| 25 | The last digit of a giantPatterns | Medium | Lemma | ||
| 60 | A hidden common factorDivisibility | Medium | Lemma | ||
| 569 | Always divisibleDivisibility | Medium | Lemma | ||
| 1123 | Weighing ten thousand poundsDivisibility | Medium | Hall & Knight | ||
| 1124 | Perfect‑cube in large basesDivisibility | Medium | Hall & Knight | ||
| 1126 | Square of repeated digit in consecutive baseDivisibility | Medium | Hall & Knight | ||
| 1127 | Digit‑rearrangement differenceDivisibility | Medium | Hall & Knight | ||
| 1128 | Divisibility by $r+1$ for symmetric digitsDivisibility | Medium | Hall & Knight | ||
| 1129 | Digit‑sum differenceDivisibility | Medium | Hall & Knight | ||
| 1130 | Triple‑repeat divisibilityDivisibility | Medium | Hall & Knight | ||
| 1131 | Parity of digit sum in odd radixDivisibility | Medium | Hall & Knight | ||
| 3 | A sum that's never wholeDivisibility | Deep | Lemma | ||
| 37 | Zeros at the end of 100!Factorials | Deep | Lemma | ||
| 62 | The last two digits of a giantPatterns | Deep | Lemma | ||
| 1132 | Repeating‑digit divisorDivisibility | Deep | Hall & Knight |
From open sources
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