Is 57 a Prime Number?

There are many tests to find if 57 is a prime number or not. We can see that 57 has 4 divisors: 1, 3, 19 and 57. But a prime number has only 2 factors. So, 57 cannot be a prime number.
 

Here are some methods that can prove why 57 is not a prime number. Let us look at these methods and learn them step by step

In this method, we will find out the number of divisors that can divide the given number evenly. Based on the count of divisors, we will categorize the number as either prime or composite.

If the count of divisors is 2, then the number is a prime number. 

If the count of divisors is more than 2 then the number is composite.

Step 1: Note that every number, including 57, is divisible by 1.

Step 2: Divide 57 by 2, as it is not divisible by 2. So 2 is not a factor of 57.

Step 3: Then divide 57 by 3 and it can be divided by 3. So 3 is a factor of 57.

Step 4: Likewise, we have to check up to the square root of 57.

√57 = 7.54983 = 7 (approximately)

Step 5: As we can find, 57 is divided by 3 and 19.

Hence, 57 is not a prime number, because 57 has more than 2 divisors.
 

We will be checking the divisibility of 57 by a set of numbers. If divisible by any of the numbers, 57 is not a prime number.

Divisibility by 2: For a number to be divisible by 2, it has to be an even number. But 57 is not an even number. Hence, it is not divisible by 2. 

Divisibility by 3: The number should be a multiple of 3 to be divisible by 3. We have to add 5 and 7, to check. We get 12 after adding 5 and 7. Likewise, we can see that 12 is a multiple of 3. This shows that 57 is divisible by 3.

Divisibility by 5: 57 is not divisible by 5 as it does not end with 0 or 5.

This shows that 57 is divisible by 3, apart from 1 and 57. Since this violates the rules of a prime number, 57 is not a prime number.
 

First let us look at the prime numbers from 1 to 100: 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. As we can see, 57 does not appear in the list. This confirms that 57 is not a prime number.
 

Prime factorization is a method in which the number is represented in the product of its prime numbers. For instance, 57 is a composite number because it has a prime factor of 3. Indeed, 57 can be presented as 3 × 19 = 57, and thus showing it has factors other than 1 and 57.
 

• Prime Factorization: Prime factorization is one of the methods in which a number is expressed as the product of its prime factors. For example, the prime factorization of 6 is 2×3

• Multiple:  It is the number when multiplied to another number, so multiple is the product of two numbers. 57, 114, 171, 228, and 285 are the multiples of 57.

• Composite numbers: Composite numbers are natural numbers that are greater than 1 and have more than 2 factors other than 1 and itself. Some examples for composite numbers are 4, 6, and 9.

• Whole Numbers: If a number is an integer, and it has no fraction, then it is called a whole number. Some examples for whole numbers are 1, 2, 3, 4, 5 and so on.