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Click to create a new example. Work through the example by deciding whether you can conclude that the given number is prime or composite using the information optained so far or whether divisibility by another prime needs to be checked.

We determine whether 1021 is prime or composite.

The square root of 1021 is approximately 31.953.

1021 mod 2 = 1, thus 1021 is not divisble by 2.

1021 mod 3 = 1, thus 1021 is not divisble by 3.

1021 mod 5 = 1, thus 1021 is not divisble by 5.

1021 mod 7 = 6, thus 1021 is not divisble by 7.

1021 mod 11 = 9, thus 1021 is not divisble by 11.

1021 mod 13 = 7, thus 1021 is not divisble by 13.

1021 mod 17 = 1, thus 1021 is not divisble by 17.

1021 mod 19 = 14, thus 1021 is not divisble by 19.

1021 mod 23 = 9, thus 1021 is not divisble by 23.

1021 mod 29 = 6, thus 1021 is not divisble by 29.

1021 mod 31 = 29, thus 1021 is not divisble by 31.

Because 1021 is not divisible by any of the primes less than or equal to its square root it is prime.