1721is an odd number,as it is not divisible by 2
The factors for 1721 are all the numbers between -1721 and 1721 , which divide 1721 without leaving any remainder. Since 1721 divided by -1721 is an integer, -1721 is a factor of 1721 .
Since 1721 divided by -1721 is a whole number, -1721 is a factor of 1721
Since 1721 divided by -1 is a whole number, -1 is a factor of 1721
Since 1721 divided by 1 is a whole number, 1 is a factor of 1721
Multiples of 1721 are all integers divisible by 1721 , i.e. the remainder of the full division by 1721 is zero. There are infinite multiples of 1721. The smallest multiples of 1721 are:
0 : in fact, 0 is divisible by any integer, so it is also a multiple of 1721 since 0 × 1721 = 0
1721 : in fact, 1721 is a multiple of itself, since 1721 is divisible by 1721 (it was 1721 / 1721 = 1, so the rest of this division is zero)
3442: in fact, 3442 = 1721 × 2
5163: in fact, 5163 = 1721 × 3
6884: in fact, 6884 = 1721 × 4
8605: in fact, 8605 = 1721 × 5
etc.
It is possible to determine using mathematical techniques whether an integer is prime or not.
for 1721, the answer is: yes, 1721 is a prime number because it only has two different divisors: 1 and itself (1721).
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 1721). 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 41.485 ). 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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