In addition we can say of the number 20 that it is even
20 is an even number, as it is divisible by 2 : 20/2 = 10
The factors for 20 are all the numbers between -20 and 20 , which divide 20 without leaving any remainder. Since 20 divided by -20 is an integer, -20 is a factor of 20 .
Since 20 divided by -20 is a whole number, -20 is a factor of 20
Since 20 divided by -10 is a whole number, -10 is a factor of 20
Since 20 divided by -5 is a whole number, -5 is a factor of 20
Since 20 divided by -4 is a whole number, -4 is a factor of 20
Since 20 divided by -2 is a whole number, -2 is a factor of 20
Since 20 divided by -1 is a whole number, -1 is a factor of 20
Multiples of 20 are all integers divisible by 20 , i.e. the remainder of the full division by 20 is zero. There are infinite multiples of 20. The smallest multiples of 20 are:
It is possible to determine using mathematical techniques whether an integer is prime or not.
for 20, the answer is: No, 20 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 20). 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 4.472 ). 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: 23