Prime Number Calculator

This prime number calculator will tell you if a particular number is prime or composite. If the number is composite, the calculator will also show all factors.

For any integer less than 10,000,000,000,000, or for any whole number greater than 13 digits, test for a prime.

A prime number can be defined as an integer, or the whole number, that is greater than 1 and not divisible either by 1 or itself. Also, a prime number can only have one factor: 1 and itself.

Prime numbers are positive numbers, non-zero numbers, that have exactly two factors -- not more or less.

Is 2 a prime number? 2 is a prime number as it only has one factor, 1 and 2.

Is 17 a prime number? Yes, 17 is a prime number, because it only has 2 factors, 1 & 17.

Is 51 a prime number? 51 is not considered a prime because it contains more than two factors. 51 is a compound number. It can be factored using any of these numbers: 1, 3, 17 51.

In the third century B.C. The third century B.C. saw the discovery of a simple method to find the prime numbers by Eratosthenes, a Greek mathematician.

Follow these steps to find prime numbers between 1 & 100.

Step 1: Create a hundred charts.

Step 2: Leave 1 because it is not a prime number or a composite number.

Step 3: Encircle 2, and then cross out any multiples, as they are not prime.

Step 4: Circle the next uncrossed figure, which is 3, and cross out any multiples. Do not ignore previously crossed numbers, such as 6, 12, 18, etc.

Step 5: Continue to encircle the next number uncrossed and cross out its multiples until all numbers in the table have been crossed or encircled.

Co-Primes: Two numbers are considered coprime if they share only one factor, which is 1. These numbers do not have to be prime. 9 and 10 for example are co-primes.

You will notice that any pair of prime numbers is always co-primes. Because of the two factors they share, their common factor cannot exceed 1. 

Twin-Primes A pair of prime numbers is known as twin primes if only one composite number exists between them. For example, (3, 5), (5, 7), (11, 13), (17, 19), etc.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97

There are 25 prime numbers that range from 1 to 100.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199.

There are 46 prime numbers that range from 1 to 200.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997.

One is not a prime or composite number.

Prime numbers can't be negative. Prime numbers are part of the natural number set.

Any even number greater than 2 is multiplied by 2. Therefore, 2 is the only prime even number.

Prime numbers have exactly two factors: 1 and the prime number. The common factor for co-prime numbers is only 1.

As of September 2021, the largest prime number is 282,589.933 - 1. This number has 24,862,048 numbers. It could be larger by the time you finish reading this.