To determine if 91 is a prime number, we can check if it is divisible by any prime numbers up to the square root of 91 (which is approximately 9.5).
We check the prime numbers 2, 3, 5, and 7:
- **2**: 91 is an odd number, so it is not divisible by 2.
- **3**: The sum of the digits (9 + 1 = 10) is not divisible by 3, so 91 is not divisible by 3.
- **5**: 91 does not end in 0 or 5, so it is not divisible by 5.
- **7**: If we divide 91 by 7, we get exactly 13 (7 × 13 = 91).
Since 91 can be divided evenly by 7 and 13, it has divisors other than 1 and itself. Therefore, it is a composite number, not a prime number.
[No]