In addition we can say of the number 18 that it is even
18 is an even number, as it is divisible by 2 : 18/2 = 9
The factors for 18 are all the numbers between -18 and 18 , which divide 18 without leaving any remainder. Since 18 divided by -18 is an integer, -18 is a factor of 18 .
Since 18 divided by -18 is a whole number, -18 is a factor of 18
Since 18 divided by -9 is a whole number, -9 is a factor of 18
Since 18 divided by -6 is a whole number, -6 is a factor of 18
Since 18 divided by -3 is a whole number, -3 is a factor of 18
Since 18 divided by -2 is a whole number, -2 is a factor of 18
Since 18 divided by -1 is a whole number, -1 is a factor of 18
Multiples of 18 are all integers divisible by 18 , i.e. the remainder of the full division by 18 is zero. There are infinite multiples of 18. The smallest multiples of 18 are:
It is possible to determine using mathematical techniques whether an integer is prime or not.
for 18, the answer is: No, 18 is not a prime number.
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 18). 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 4.243 ). 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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Next prime number: 19