1. The problem is to identify which numbers among 49, 47, 13, and 21 are prime. 2. A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. 3. Check each number: - 49: Divisible by 7 (since $7 \times 7 = 49$), so not prime. - 47: Check divisibility by primes less than $\sqrt{47} \approx 6.85$ (2, 3, 5). 47 is not divisible by 2, 3, or 5, so 47 is prime. - 13: Check divisibility by primes less than $\sqrt{13} \approx 3.6$ (2, 3). 13 is not divisible by 2 or 3, so 13 is prime. - 21: Divisible by 3 and 7 (since $3 \times 7 = 21$), so not prime. 4. Therefore, the prime numbers are 47 and 13.