Prime Number Calculator

Need to know if a number is prime? The easiest way to find out is to use our prime number calculator thanks to which, you only have to enter the number, press the calculate button and you will automatically know if a number is prime or not.

What is a prime number?

A prime number is a number natural number greater than one and that can be to decompose into two specific factorsThis was discovered more than 2,000 years ago by Euclid, a famous Greek mathematician.

If you want to learn how to decompose a number into factorsThe link that we have just left you will show you the process to follow or factor a number online, so you can get out of doubts and to see if it is a prime number or not.

How to know if a number is prime?

Knowing if a number is prime

To calculate if a number is prime or not what we have to do is to divide it in an orderly way by all the prime numbers smaller than it.

Yes we do not obtain exact divisions and we manage to get a quotient less than or equal to the divisorthen we are dealing with a prime number.

Erastótenes sieve for finding prime numbers

There is another method based on the Sieve of Eratosthenes to find all the prime numbers less than a certain digit. The process to find all prime numbers is as follows.

The first thing we have to do is write all the numbers from 2 up to the quantity you want. For example, let's find all the primes from 2 to 50.

2345678910
11121314151617181920
21222324252627282930
31323334353637383940
41424344454647484950

Now we eliminate all those numbers that are multiples of 2:

23579
1113151719
2123252729
3133353739
4143454749

We have to repeat the previous step with the following numbers after 2 that have not been eliminated. So, now we eliminate all the multiples of 3:

2357
11131719
232529
313537
41434749

The next number from which we have to remove all its multiples is 5. To simplify the process, we will also remove the multiples of 7.

2357
11131719
2329
3137
414347

The process of searching for prime numbers with the Erastótenes Sieve ends when only prime numbers are listed..

Is 1 a prime number?

Although many of us have been taught that number 1 is prime, the truth is that the mathematical community does not currently consider it to be so. This is because the number 1 does not fulfill this premise that "every natural number has a unique representation as a product of prime factors, except for the order".

The number 1 has only one divisor: itself. Because of this, right now the number one is considered neither prime nor composite but a unit by which all natural numbers can be divided.

Smallest prime number

Taking into account the reasoning of the previous point, the smallest prime number that exists is 2.

Largest prime number

By contrast, the largest prime number known to date has a total of 22,338,618 digits and it is the 274.207.281 -1. It was discovered on January 7, 2016 and has set a new Guinness record.

This number has been discovered by Curtis Cooper, a mathematician at the University of Central Missouri located in Warrensburg (USA).

Will a prime number larger than this one appear? Yes, it's only a matter of time. Computers and special software are being used all day long to find larger prime numbers. What's more, the group dedicated to this type of discovery has assured that it will not rest until it finds a prime number with 100 million digits.

Prime numbers from 1 to 100

Below you will find a table that shows the prime numbers from 1 to 100You can tell them apart because they are highlighted in red. The rest are not prime numbers:

123456
789101112
131415161718
192021222324
252627282930
313233343536
373839404142
434445464748
495051525354
555657585960
616263646566
676869707172
737475767778
798081828384
858687888990
919293949596
979899100

4 thoughts on “Calculadora de números primos”

    • Hello Harry,

      Thank you very much for your feedback. We have checked with some values ending in 5 and indeed it failed. Thanks for the warning.

      We have already solved it and in passing we have taken the opportunity to indicate the number by which it is divisible in case it is not a prime number.

      Greetings!

  1. I am just starting to program with PYTHON.
    This is the code... Very elementary but it works!

    num=int(input("Enter a number :"))
    if num==2:
    print(num,"...ES is PRIMO")

    denomin=2
    while denom>=2 and denom<num : # sweeps from 2 to <num
    mod_cociente=num%denom # saca el módulus
    if mod_quotient ==0 :
    print(mod_quotient)
    print(num,"...is NOT prime :It is divisible by :", denom)
    break
    else:
    print(mod_quotient)
    print(num,"...ES is PRIMO")
    denomin=denom+1
    # Print multiple answers.VALID LAST!!!

    Reply

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