6991is an odd number,as it is not divisible by 2
The factors for 6991 are all the numbers between -6991 and 6991 , which divide 6991 without leaving any remainder. Since 6991 divided by -6991 is an integer, -6991 is a factor of 6991 .
Since 6991 divided by -6991 is a whole number, -6991 is a factor of 6991
Since 6991 divided by -1 is a whole number, -1 is a factor of 6991
Since 6991 divided by 1 is a whole number, 1 is a factor of 6991
Multiples of 6991 are all integers divisible by 6991 , i.e. the remainder of the full division by 6991 is zero. There are infinite multiples of 6991. The smallest multiples of 6991 are:
0 : in fact, 0 is divisible by any integer, so it is also a multiple of 6991 since 0 × 6991 = 0
6991 : in fact, 6991 is a multiple of itself, since 6991 is divisible by 6991 (it was 6991 / 6991 = 1, so the rest of this division is zero)
13982: in fact, 13982 = 6991 × 2
20973: in fact, 20973 = 6991 × 3
27964: in fact, 27964 = 6991 × 4
34955: in fact, 34955 = 6991 × 5
etc.
It is possible to determine using mathematical techniques whether an integer is prime or not.
for 6991, the answer is: yes, 6991 is a prime number because it only has two different divisors: 1 and itself (6991).
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 6991). 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 83.612 ). 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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