Previous prime number

Client

Walk downward from n−1 to find the previous prime.

About Previous prime number

Largest prime strictly less than n. The interactive transform on this page runs in your browser tab—Toolcore does not need your paste for the core operation described above.

How to use this page

Paste or type in the main workspace, run the primary action from the toolbar, then copy or download the result. Use Load example when the page offers it, or URL prefill (?q= / ?qb=) so agents and tickets open the same input.

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Nearby workflows on Toolcore

  • Next prime number — Smallest prime strictly greater than n. when units or numeric output should be checked on a related calculator.
  • Prime gap calculator — Gap to the next prime after a given prime n. when units or numeric output should be checked on a related calculator.
  • Prime number checker — Test whether a whole number is prime—BigInt trial division in your browser, no upload. when units or numeric output should be checked on a related calculator.
  • Prime factorization — Factor whole numbers into prime products—BigInt trial division in your browser, no upload. when units or numeric output should be checked on a related calculator.

Common use cases

  • Previous prime number for quick local checks without uploading data.
  • Copy results into tickets, docs, or classroom notes.

Common mistakes to avoid

  • Unexpected input shape

    See the intro and how-to notes for accepted formats.

FAQ

Is processing local?

Yes—this runs entirely in your browser.

Agent prefill?

Use q or qb for the main text field when supported.

More tools

Related utilities you can open in another tab—mostly client-side.