Is 248 a Prime Number?

There are two types of numbers, mostly — Prime numbers and composite numbers, depending on the number of factors.

A prime number is a natural number that is divisible only by 1 and itself. For example, 3 is a prime number because it is divisible by 1 and itself.

A composite number is a positive number that is divisible by more than two numbers. For example, 6 is divisible by 1, 2, 3, and 6, making it a composite number.

Prime numbers follow few properties like:

• Prime numbers are positive numbers always greater than 1.
  
   
• 2 is the only even prime number.
  
   
• They have only two factors: 1 and the number itself.
  
   
• Any two distinct prime numbers are co-prime numbers because they have only one common factor, which is 1. As 248 has more than two factors, it is not a prime number.

The characteristic of a prime number is that it has only two divisors: 1 and itself. Since 248 has more than two factors, it is not a prime number. A few methods are used to distinguish between prime and composite numbers:

• Counting Divisors Method
• Divisibility Test
• Prime Number Chart
• Prime Factorization

The method in which we count the number of divisors to categorize the numbers as prime or composite is called the counting divisors method. Based on the count of the divisors, we categorize prime and composite numbers.

- If there is a total count of only 2 divisors, then the number would be prime.

- If the count is more than 2, then the number is composite.

Let’s check whether 248 is prime or composite.

Step 1: All numbers are divisible by 1 and itself.

Step 2: Divide 248 by 2. It is divisible by 2, so 2 is a factor of 248.

Step 3: Divide 248 by 3. It is not divisible by 3, so 3 is not a factor of 248.

Step 4: You can simplify checking divisors up to 248 by finding the root value. We then need to only check divisors up to the root value.

Step 5: When we divide 248 by 2, 4, and 8, it is divisible by 2, 4, and 8. Since 248 has more than 2 divisors, it is a composite number.

We use a set of rules to check whether a number is divisible by another number completely or not, which is called the Divisibility Test Method.

- Divisibility by 2: The number in the one's place value is 8. Since 8 is an even number, 248 is divisible by 2.

- Divisibility by 3: The sum of the digits in the number 248 is 14. Since 14 is not divisible by 3, 248 is also not divisible by 3.

- Divisibility by 5: The unit's place digit is not 0 or 5, so 248 is not divisible by 5.

- Divisibility by 7: To check divisibility by 7, double the last digit (8 × 2 = 16) and subtract it from the rest of the number (24 - 16 = 8). Since 8 is not divisible by 7, 248 is also not divisible by 7.

- Divisibility by 11: In 248, the difference between the sum of the digits in odd positions (2 + 8) and the sum of the digits in even positions (4) is 6, which is not divisible by 11.

Since 248 is divisible by more than just 1 and itself, it is a composite number.

The prime number chart is a tool created using a method called “The Sieve of Eratosthenes.” In this method, we follow these steps:

Step 1: Write numbers from 1 to 100 in 10 rows and 10 columns.

Step 2: Leave 1 without coloring or crossing, as it is neither prime nor composite.

Step 3: Mark 2 because it is a prime number and cross out all the multiples of 2.

Step 4: Mark 3 because it is a prime number and cross out all the multiples of 3.

Step 5: Repeat this process until you reach the table consisting of marked and crossed boxes, except 1. Through this process, we will have a list of prime numbers from 1 to 100.

The list is 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, and 97. 248 is not present in the list of prime numbers, so it is a composite number.

Prime factorization is a process of breaking down a number into prime factors and then multiplying those factors to obtain the original number.

Step 1: We can write 248 as 2 × 124.

Step 2: In 2 × 124, 124 is a composite number. Further, break the 124 into 2 × 62.

Step 3: 62 is also a composite number, and it can be further broken into 2 × 31.

Step 4: Now we get the product consisting of only prime numbers. Hence, the prime factorization of 248 is 2 × 2 × 2 × 31.

- Composite numbers: Natural numbers greater than 1 that are divisible by more than 2 numbers are called composite numbers. For example, 12 is a composite number because it is divisible by 1, 2, 3, 4, 6, and 12.

- Prime numbers: Numbers greater than 1 that are only divisible by 1 and themselves. For example, 5 is a prime number because it is only divisible by 1 and 5.

- Factors: The numbers that divide the number exactly without leaving a remainder are called factors. For example, the factors of 8 are 1, 2, 4, and 8 because they divide 8 completely.

- Divisibility rules: A set of rules that help to determine whether one number is divisible by another without performing the division.

- Prime factorization: The process of expressing a number as the product of its prime factors. For example, the prime factorization of 18 is 2 × 3 × 3.