Is 358 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 a 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 358 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 358 has more than two factors, it is not a prime number. Few methods are used to distinguish between prime and composite numbers. A few methods are: -

1. Counting Divisors Method 
2. Divisibility Test 
3. Prime Number Chart 
4. 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 358 is prime or composite.

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

Step 2: Divide 358 by 2. It is divisible by 2, so 2 is a factor of 358.

Step 3: Divide 358 by 3. It is not divisible by 3, so 3 is not a factor of 358.

Step 4: You can simplify checking divisors up to 358 by finding the square root value. We then need to only check divisors up to the square root value.

Step 5: When we divide 358 by 2 and 179, it is divisible by both. Since 358 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. It is called the Divisibility Test Method. -

Divisibility by 2: The number in the ones' place value is 8. Eight is an even number, which means that 358 is divisible by 2. 

Divisibility by 3: The sum of the digits in the number 358 is 16. Since 16 is not divisible by 3, 358 is also not divisible by 3. 

Divisibility by 5: The unit’s place digit is 8. Therefore, 358 is not divisible by 5. 

Divisibility by 7: Double the last digit (8 × 2 = 16) and subtract it from the rest of the number (35 - 16 = 19). Since 19 is not divisible by 7, 358 is also not divisible by 7. 

Divisibility by 11: In 358, the difference between the sum of the digits in odd positions (3 + 8 = 11) and the sum of the digits in even positions (5) is 6. This means that 358 is not divisible by 11.

Since 358 is divisible only by 2 and 179, it has more than two factors. Therefore, it is a composite number.

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

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

Step 2: Leave 1 unmarked, 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. 358 is not present in this list, so it is a composite number.

Prime factorization is a process of breaking down a number into prime factors. Then multiply those factors to obtain the original number.

Step 1: We can write 358 as 2 × 179.

Step 2: In this factorization, 179 is a prime number.

Step 3: Therefore, the prime factorization of 358 is 2 × 179.

• 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 12 is divisible by 1, 2, 3, 4, 6, and 12.

• Prime numbers: A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.

• Divisibility: A number is divisible by another if, after division, the remainder is zero.

• Sieve of Eratosthenes: An ancient algorithm used to find all prime numbers up to a specified integer.

• Prime factorization: The process of expressing a composite number as a product of its prime factors.