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Next and Previous Prime Finder
Find strictly previous and next primes within a chosen finite radius and download every tested candidate and search-bound status.
Integer decimal text, Search radius decimal text
nearest-primes.json
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Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
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How to use this tool
- Enter an unsigned integer from 2 to 1,000,000,000,000 and a search radius from 1 to 1,000.
- Select Find previous and next primes. The entered number is excluded; candidates are tried by increasing distance, previous before next.
- Download nearest-primes.json to inspect both directional bounds, statuses and every tested candidate.
Examples
1000 with radius 100 finds previous prime 997 and next prime 1009.
Limitations
- At most 64 input UTF-16 units, 2,000 candidate calls, 2,000,000 conservative divisor-work units, 1 MiB complete output and 30 seconds.
- Candidate domain is 2 through 1,000,000,000,000. FOUND, NOT_FOUND_WITHIN_BOUND and DOMAIN_BOUND have different meanings; a bounded search does not promise both primes.
- Before each candidate, charge floor(sqrt(candidate)). Near 1,000,000,000,000 roughly two charges exhaust the budget; exceeding it refuses the complete operation without a partial report.
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