What This Calculator Does

This page is best for three related tasks. First, deciding whether an integer is prime. Second, factoring a number into its prime factors. Third, listing every prime in a selected interval. Because those three tools live together, the page works well for classroom practice, early number theory study, contest prep, and quick verification.

Unlike pages that return only one yes-or-no answer, this one also shows nearby primes, smallest factor, or divisor count depending on the mode. That makes it more useful for understanding the number, not just labeling it.

When to Use It

• You want to know whether a specific integer is prime.
• You want the prime factorization of a number.
• You want every prime inside a chosen range.
• You want context about the nearest surrounding primes.

Inputs Explained

Mode

The current page supports three modes.

• check for primality testing
• factor for prime factorization
• range for listing all primes in an interval

Single Number