Select all prime numbers from the list: 11, 15, 17, 21.
Note
11 and 17 are prime because they have no positive divisors other than 1 and themselves; 15 and 21 are composite (15 = 3 × 5, 21 = 3 × 7).
Select all prime numbers from the list: 11, 15, 17, 21.
11 and 17 are prime because they have no positive divisors other than 1 and themselves; 15 and 21 are composite (15 = 3 × 5, 21 = 3 × 7).