Prime Number Checker
Primes · Class V
Is your number prime?
17
type a value
2100
Live values
- Number17
- Smallest factor > 117
- Prime? (1 = yes)1
Live readout
Number17
Smallest factor > 117
Prime? (1 = yes)1
Number17
Formulas in this lab
- Number
- Smallest factor > 1
- Prime? (1 = yes)
Tip: A prime has exactly two factors: 1 and itself!
Frequently asked questions
▶What is a prime number?
A prime number has exactly two factors: 1 and itself. So 7 is prime because only 1 and 7 divide it. 6 is not prime because 1, 2, 3 and 6 all divide it.
▶How do I use the prime checker?
Pick a number using the slider. The lab tests every smaller number to see if it divides cleanly. If only 1 and the number itself work, then it is prime.
▶When are prime numbers useful?
Primes are the building blocks of all whole numbers. Every other number can be made by multiplying primes. They are also used to keep online passwords and UPI payments safe in real life.
▶Did you know about primes?
The first primes are 2, 3, 5, 7, 11, 13. The number 2 is the only even prime; all other primes are odd. There are infinitely many primes, but they get rarer as numbers grow.