# Is 21 Prime Number or Composite Number

Created by: Team Maths - Examples.com, Last Updated: July 31, 2024

## Is 21 a Prime Number?

### No – 21 is not a Prime Number.

Why No: 21 is not a prime number because it does not meet the prime criteria of having exactly two distinct positive divisors: 1 and itself. See any number if it’s prime number or not.

## Is 21 a Composite Number?

### Yes – 21 is a Composite Number.

Why Yes: 21 is a composite number because it has more than two distinct positive divisors. It has 1, 3, 7, and itself (21).

## Problem Statements

Property Answer
Is 21 a prime number? No
Is 21 a composite number? Yes
Is 21 a perfect square? No
Factors of 21 1, 3, 7, 21
Multiples of 21 21, 42, 63, 84, 105, 126, 147, 168, 189, 210
Cube Root of 21 2.76
Square of 21 441
Square Root of 21 4.58
Is 21 a Perfect Square? No
Is 21 a Perfect Cube? No
Is 21 an Irrational number No
Is 21 a Rational number Yes
Is 21 a Real number Yes
Is 21 an Integer Yes
Is 21 a Natural number Yes
Is 21 a Whole number Yes
Is 21 an Even or odd number Yes (21 is an odd number)
Is 21 an Ordinal number Yes
Is 21 a Complex number Yes (as all real numbers are also complex numbers)

## What are the factors of 21?

The factors of 21 are 1, 3, 7, and 21. 21 is not a prime number because it is divisible by numbers other than 1 and itself, highlighting its composite nature. There are multiple factors of 21, making it clear that it is not a prime number.

## What Kind of Number is 21?

• 21 is a composite number.
• 21 is one of the odd numbers; it is an odd number.
• 21 is considered significant in various cultures, potentially for its numerical properties.
• 21 is a natural number.
• 21 is a positive integer.
• 21 is a composite number.
• 21 is an odd number.
• 21 is a rational number.
• 21 is a whole number.

21 is recognized as a composite number because it has more than two divisors: 1, 3, 7, and itself (21). This characteristic distinguishes it from prime numbers, which have exactly two divisors. The number 21, while it may not hold the same type of cultural or numerical significance as 20 in terms of counting systems, is primarily noted in mathematics for its composite status. Its properties as an odd, composite, and natural number make it a noteworthy figure in various mathematical and conceptual frameworks.

## What is the 21st prime number?

The 21st prime number is 73. Prime numbers are those that have only two distinct positive divisors: 1 and themselves, and 73 fits this definition.

## What is the composite of 21?

The composite of 21 refers to its factors other than 1 and itself, which are 3 and 7. A composite number has more than two divisors.

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