31981is an odd number,as it is not divisible by 2
The factors for 31981 are all the numbers between -31981 and 31981 , which divide 31981 without leaving any remainder. Since 31981 divided by -31981 is an integer, -31981 is a factor of 31981 .
Since 31981 divided by -31981 is a whole number, -31981 is a factor of 31981
Since 31981 divided by -1 is a whole number, -1 is a factor of 31981
Since 31981 divided by 1 is a whole number, 1 is a factor of 31981
Multiples of 31981 are all integers divisible by 31981 , i.e. the remainder of the full division by 31981 is zero. There are infinite multiples of 31981. The smallest multiples of 31981 are:
0 : in fact, 0 is divisible by any integer, so it is also a multiple of 31981 since 0 × 31981 = 0
31981 : in fact, 31981 is a multiple of itself, since 31981 is divisible by 31981 (it was 31981 / 31981 = 1, so the rest of this division is zero)
63962: in fact, 63962 = 31981 × 2
95943: in fact, 95943 = 31981 × 3
127924: in fact, 127924 = 31981 × 4
159905: in fact, 159905 = 31981 × 5
etc.
It is possible to determine using mathematical techniques whether an integer is prime or not.
for 31981, the answer is: yes, 31981 is a prime number because it only has two different divisors: 1 and itself (31981).
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 31981). 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 178.832 ). 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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