what exactly is a prime number? simple answers please!!?

Answer 1

A prime number is a number larger than 1 that is only divisible by itself or one.
Thus 17 is a prime number since the only factorization of 17 is 17 = 17 × 1
15 is not a prime number because it can be divided equally by three, five, one or fifteen.

Answer 2

1 is NOT, repeat NOT a prime number.

The interesting question is "Why?", and the answer is "Because it would get in the way".

1 does indeed meet the criteria of being divisible by only itself and 1. However, if we allow 1 to be a prime number, then lots and lots of theorems that mention "prime numbers" would have to instead says "prime numbers (other than 1)". So really it's for convenience's sake that we exclude 1 from the set of prime numbers.

An example - the fundamental theorem of arithmetic states that any integer can be factored into a unique set of primes, e.g.
120 = 2 x 2 x 2 x 3 x 5

If we allowed 1 as a prime, then the uniqueness bit doesn't work any more, and we have a much less useful theorem:
120 = 2 x 2 x 2 x 3 x 5
120 = 2 x 2 x 2 x 3 x 5 x 1
120 = 2 x 2 x 2 x 3 x 5 x 1 x 1
120 = 2 x 2 x 2 x 3 x 5 x 1 x 1 x 1
...etc.

Answer 3

Prime Number is a whole number that can only be divisible by 1 or the number itself.

Prime Numbers: 2, 3, 5, 7, 11, 13, 17, 19, 23.....

Lets take the number 7 for example. So, the first question that you would ask is "what can 7 be divisible by?". so, we know that 1 x 7 is 7, then 2 will be multiplied by what number to give us 7, the answer would be none because 2 x 3 is 6 and 2 x 4 is 8. Then, 7 can only be divisible by 7 or 1. That example would go for all the prime numbers you see above

Answer 4

At one time 1 was considered prime, but mathematicians today use a different definition of prime so that it is not considered prime. By definition: A number is prime if it has exactly TWO factors (1 and itself). By this definition, 1 has only ONE factor and is not prime. (Note: It is also not composite, because composite numbers have MORE than two factors) The formal reason is that lots of other math requires that we don't consider 1 a prime number. One reason is the "Fundamental Theorem of Arithmetic" which says, "Every positive integer can be written uniquely as a product of primes, with the prime factors in the product written in order of nondecreasing size." As you can see, if 1 was considered prime, you could no longer write a number uniquely as a product of primes. Today where were write something like: 30 = 2 x 3 x 5 You'd also have: 30 = 1 x 2 x 3 x 5 30 = 1 x 1 x 2 x 3 x 5 etc. Therefore mathematicians decided to change the definition so that one is not considered prime (or composite).

Answer 5

a prime number is a number that can only be divided by the number 1 and itself
2 is a prime number because 2/1 is 2 and 2/2 is 1

Answer 6

A number which can only be divided by itself and 1.

Ex. 2 = 2*1
2 is a prime number, in fact the smallest.

Ex. 6 = 2*3 (as well as 1*6);
So 6 is not a prime number, since the divisors include 2 & 3.

Note: all numbers can be expressed as product of itself and 1; so, we are interested in all other divisors or factors.

Answer 7

its a number that cant be divided by another number apart from 1.So 1 , 3 , 5 ,7 are all prime numbers. 8 can be divided by 2 and 4 so it is not a prime number

Answer 8

A prime number is a number that is divisible by itself and one. Some examples are 2, 3, 5, 7, 11, 13, 17 and so on.

Answer 9

ok, so many people do not know what a prime number is!!

here is a definitive answer,.

a number is prime if it has EXACTLY 2 factors!!

Obviously 1 is a factor of every number, and any number is a factor of itself, therefore the two factors are 1 and the number itself.

however since a prime number is defined as having EXACTLY TWO factors then ONE is NOT prime, as it only has one factor.

the first prime number is TWO, then THREE, then FIVE, then SEVEN then ELEVEN...

at the moment there is no proof about the distribution of the prime numbers but the Riemann Hypothesis is waiting to be proved, and if it is it will make whoever does an international superstar, just like Prof Andrew Wiles!!

Answer 10

A number that is ONLY divisible by one and itself.
So the series of prime numbers will begin with 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37...