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Is 31 a prime number?

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Is 31 a prime or composite number?

Answer

Number 31 is a Prime

31 has exactly two divisors — 1 and 31 — so it is a prime.

Primes up to √31

5² = 25 ≤ 31 < 36 = 6², so it is enough to try primes up to 5

÷2 does not divide
÷3 does not divide
÷5 does not divide

none of the 3 primes up to 5 divides 31 — 31 is prime

Nearest primes: 29 and 37

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See Also

Factors of a Number - List all Factors and Factor Pairs of a Number
Prime Factorization - Prime Factorization Calculator
Prime Numbers List - List of all Prime Numbers - how many Prime numbers are between

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Is 31 a prime number? Is 31 a prime number? 31 is a prime number. Check if any number is prime or composite with our free online prime checker.

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Prime numbers list

Number	Is Prime
16	No: 2⁴
17	Yes
18	No: 2 × 3²
19	Yes
20	No: 2² × 5
21	No: 3 × 7
22	No: 2 × 11
23	Yes
24	No: 2³ × 3
25	No: 5²
26	No: 2 × 13
27	No: 3³
28	No: 2² × 7
29	Yes
30	No: 2 × 3 × 5
31	Yes
32	No: 2⁵
33	No: 3 × 11
34	No: 2 × 17
35	No: 5 × 7
36	No: 2² × 3²
37	Yes
38	No: 2 × 19
39	No: 3 × 13
40	No: 2³ × 5
41	Yes
42	No: 2 × 3 × 7
43	Yes
44	No: 2² × 11
45	No: 3² × 5

FAQ

Is 31 a prime or composite number?

Number 31 is a Prime

How many factors are in a number 31?

2

How to check if 31 is prime?

Divide 31 by the primes in order: 5² = 25 ≤ 31 < 36 = 6², so it is enough to try primes up to 5. None of the 3 primes up to 5 divides 31, so 31 is prime.