331is an odd number,as it is not divisible by 2
The factors for 331 are all the numbers between -331 and 331 , which divide 331 without leaving any remainder. Since 331 divided by -331 is an integer, -331 is a factor of 331 .
Since 331 divided by -331 is a whole number, -331 is a factor of 331
Since 331 divided by -1 is a whole number, -1 is a factor of 331
Since 331 divided by 1 is a whole number, 1 is a factor of 331
Multiples of 331 are all integers divisible by 331 , i.e. the remainder of the full division by 331 is zero. There are infinite multiples of 331. The smallest multiples of 331 are:
0 : in fact, 0 is divisible by any integer, so it is also a multiple of 331 since 0 × 331 = 0
331 : in fact, 331 is a multiple of itself, since 331 is divisible by 331 (it was 331 / 331 = 1, so the rest of this division is zero)
etc.
It is possible to determine using mathematical techniques whether an integer is prime or not.
for 331, the answer is: yes, 331 is a prime number because it only has two different divisors: 1 and itself (331).
To know the primality of an integer, we can use several algorithms. The most naive is to try all divisors below the number you want to know if it is prime (in our case 331). We can already eliminate even numbers bigger than 2 (then 4 , 6 , 8 ...). Besides, we can stop at the square root of the number in question (here 18.193 ). Historically, the Eratosthenes screen (which dates back to Antiquity) uses this technique relatively effectively.
More modern techniques include the Atkin screen, probabilistic tests, or the cyclotomic test.
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