Is 82 a Prime Number?

There are two types of numbers, mostly —

• Prime numbers
   
• 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 82 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 82 has more than two factors, it is not a prime number. A few methods are used to distinguish between prime and composite numbers. A few methods are:

• 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 82 is prime or composite.

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

Step 2: Divide 82 by 2. It is divisible by 2, so 2 is a factor of 82.

Step 3: Divide 82 by 3. It is not divisible by 3, so 3 is not a factor of 82.

Step 4: You can simplify checking divisors up to 82 by finding the root value. We then need to only check divisors up to the root value.

Step 5: When we divide 82 by 2 and 41, it is divisible by both. Since 82 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 2. Two is an even number, which means that 82 is divisible by 2.

Divisibility by 3: The sum of the digits in the number 82 is 10. Since 10 is not divisible by 3, 82 is also not divisible by 3.

Divisibility by 5: The unit’s place digit is 2. Therefore, 82 is not divisible by 5.

Divisibility by 7: To check divisibility by 7, double the last digit (2 × 2 = 4). Then, subtract it from the rest of the number (8 - 4 = 4). Since 4 is not divisible by 7, 82 is also not divisible by 7.

Divisibility by 11: In 82, the sum of the digits in odd positions is 8, and the sum of the digits in even positions is 2. Their difference is 6, which means that 82 is not divisible by 11.

Since 82 is divisible by 2 and 41, 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 the following steps.

Step 1: Write 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.

82 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. Then multiply those factors to obtain the original number.

Step 1: We can write 82 as 2 × 41. Step 2: Both 2 and 41 are prime numbers.

Hence, the prime factorization of 82 is 2 × 41.

• Composite numbers: Natural numbers greater than 1 that are divisible by more than 2 numbers are called composite numbers. For example, 82 is a composite number because 82 is divisible by 1, 2, 41, and 82
   
• Prime numbers: Natural numbers greater than 1 that are divisible only by 1 and themselves.
   
• Factors: The numbers that divide the number exactly without leaving a remainder are called factors. For example, the factors of 4 are 1, 2, and 4 because they divide 4 completely.
   
• Divisibility: The capacity of one number to be divided by another without leaving a remainder.
   
• Sieve of Eratosthenes: An ancient algorithm used to find all prime numbers up to a specified integer.