In addition we can say of the number 28 that it is even
28 is an even number, as it is divisible by 2 : 28/2 = 14
The factors for 28 are all the numbers between -28 and 28 , which divide 28 without leaving any remainder. Since 28 divided by -28 is an integer, -28 is a factor of 28 .
Since 28 divided by -28 is a whole number, -28 is a factor of 28
Since 28 divided by -14 is a whole number, -14 is a factor of 28
Since 28 divided by -7 is a whole number, -7 is a factor of 28
Since 28 divided by -4 is a whole number, -4 is a factor of 28
Since 28 divided by -2 is a whole number, -2 is a factor of 28
Since 28 divided by -1 is a whole number, -1 is a factor of 28
Multiples of 28 are all integers divisible by 28 , i.e. the remainder of the full division by 28 is zero. There are infinite multiples of 28. The smallest multiples of 28 are:
It is possible to determine using mathematical techniques whether an integer is prime or not.
for 28, the answer is: No, 28 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 28). 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 5.292 ). 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.
Previous prime number: 23
Next prime number: 29