List of Prime Numbers from 1 to 20

We say that a number is a prime number if the only factors of that number are 1 and itself. If the number has three or more factors then we say that the number is not a prime number. Such numbers are called composite numbers. The number 1 is by definition considered to be neither a prime number nor a composite number.

Primes between 1 and 20

There are a total of 8 prime numbers between 1 and 20. These eight numbers are 2, 3, 5, 7, 11, 13, 17, and 19.

1. The number 1 is neither prime nor composite.
2. The number 2 is a prime because it has only two factors – 1 and 2.
3. The number 3 is a prime because it has only two factors – 1 and 3.
4. The number 4 is not prime because it has factors 1, 2 and 4.
5. The number 5 is a prime because it has only two factors – 1 and 5.
6. The number 6 is not prime because it has factors 1, 2, 3 and 6.
7. The number 7 is a prime because it has only two factors – 1 and 7.
8. The number 8 is not prime because it has factors 1, 2, 4 and 8.
9. The number 9 is not prime because it has factors 1, 3 and 9.
10. The number 10 is not prime because it has factors 1, 2, 5 and 10.
11. The number 11 is a prime because it has only two factors – 1 and 11.
12. The number 12 is not prime because it has factors 1, 2, 3, 4, 6 and 12.
13. The number 13 is a prime because it has only two factors – 1 and 13.
14. The number 14 is not prime because it has factors 1, 2, 7 and 14.
15. The number 15 is not prime because it has factors 1, 3, 5 and 15.
16. The number 16 is not prime because it has factors 1, 2, 4, 8 and 16.
17. The number 17 is a prime because it has only two factors – 1 and 17.
18. The number 18 is not prime because it has factors 1, 2, 3, 6, 9 and 18.
19. The number 19 is a prime because it has only two factors – 1 and 19.
20. The number 20 is not prime because it has factors 1, 2, 4, 5, 10 and 20.