Can anyone give the formula to find a prime number?

Answer 1

Not yet.

Answer 2

The Sieve of Eratosthenes

Eratosthenes (275-194 B.C., Greece) devised a 'sieve' to discover prime numbers. A sieve is like a strainer that you drain spaghetti through when it is done cooking. The water drains out, leaving your spaghetti behind. Eratosthenes's sieve drains out composite numbers and leaves prime numbers behind.
To use the sieve of Eratosthenes to find the prime numbers up to 100, make a chart of the first one hundred whole numbers (1-100):

1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 68 69 70
71 72 73 74 75 76 77 78 79 80
81 82 83 84 85 86 87 88 89 90
91 92 93 94 95 96 97 98 99 100


1. Cross out 1, because it is not prime.

2. Circle 2, because it is the smallest positive even prime. Now cross out every multiple of 2; in other words, cross out every second number.

3. Circle 3, the next prime. Then cross out all of the multiples of 3; in other words, every third number. Some, like 6, may have already been crossed out because they are multiples of 2.

4. Circle the next open number, 5. Now cross out all of the multiples of 5, or every 5th number.

5. Continue doing this until all the numbers through 100 have either been circled or crossed out. You have just circled all the prime numbers from 1 to 100!

More on Prime Numbers:

http://mathforum.org/dr.math/faq/faq.prime.num.html

Answer 3

You can decide if a number is prime by noting if it's an odd number. (Every even number can be divided by two). IF it's an odd number, determine if it can be reduced by division with a whole number. For example, 15 can be divided by 5 and by 3; so it's not a prime number. Try this same exercise on 17 and 19. Neither can be divided by a whole number, hence they are prime numbers. So to get you started here are a few prime numbers: 3, 5, 7, 11, 13, 17, 19, 23, 29, 31. Why don't you figure out what other primes there might be up to 60? Off the top of my head, I think there are 6 more.

Answer 4

there is no such formula as to find all prime numbers , since prime numbers are distributed quite randomly across the number line. However you can generate some using the formula (2^n)-1 where n is a natural number. This is because prime number is an odd number and (2^n)-1 will produce an odd number although not all generated will be prime number.

Answer 5

there is NO formula to give you a 100% sure prime number.

you can try (2^n)-1 which is OFTEN a prime (but not always, example: 15 is not prime)

If there was a formula for prime numbers, almost all cryptology algorithms would fail.
Check a good cryptology book for other formulas that will give you a "good chance" to end up with a prime.

Answer 6

there ARE formulas for finding a prime number but not for finding all prime numbers

Answer 7

Number X is said to be prime P number if
X mode P!=0 for every P(i) This is the easiest way I know to check,you can obtain thousands of primes using MS Excel
you can e-mail me if you want at [e-mail] for details.

Answer 8

there is no particular formula to find a prime number but you can write a program in c language ,it goes as follows

#include
main()
{
int n,i,c=0;
printf("enter a value");
scanf("%d",&n);
while(i<=n)
{
if(n%i==0)
{
c=c+1;
}
i++;
}
if(c==2)
printf("the given is prime");
else
printf("not");
getch();
}

when yiu type this program in c lang enter any num the program will tell whether it is prime or no.

Answer 9

Try this. Take 41, then add 2, then add 4,6,8,10,...all consecutive even numbers. This simple algorithm produces lots of primes. Enjoy.

Answer 10

Forget it. Impossible.
Th