Square root of 21

If you are looking to answer the following questions: “what is the square root of 21?” The answer is 4.5825756949558. 

ANSWER: square root of 21=4.5825756949558

The square root of a number (21 in this case) is a number (4.5825756949558 in this case) which multiplied by itself equals the number from which you are calculating the square root (21). Mathematically square root of 21 can expressed in the radical form or an exponent form as shown below:

• Radical form of the square root of 21: √21
• Exponent form of the square root of 21: (21)^½ or (21)^0.5

This symbol √ is called radical sign or radix. The number whose square root is being calculated is called the radicand. The radicand is the number underneath the radical sign (radix), in this case it is 21.

Square root of 21 calculator

If you would like to confirm the answer to the question of “what is the square root of 21?” or calculate a square root of any other number use the square root calculator:

Square root of 21 calculation guide

In the following sections we explain how to calculate the square root of 21. We will answer such common questions as: “is the square root of 21 rational or irrational?” and “is 21 a perfect square?” We will discuss what the principal square root of 21 is.  For your reference we also included the following tables:

• N^th roots of 21
• Perfect square numbers
• Square roots of numbers around 21 

You will find all the information you need on the square root of 21 calculations below. 

What is the square root of 21?

The square root of 21 is a number which multiplied by itself equals 21. Therefore, the square root of 21 is 4.5825756949558 and we write it √21=4.5825756949558 because 4.58257569495582=21. Since 4.58257569495582 is the same as 4.5825756949558 x 4.5825756949558 the following expressions is true:

21 = 4.58257569495582=4.5825756949558×4.5825756949558

Therefore

ANSWER: square root of 21=√21=4.5825756949558

Is 21 a Perfect Square?

A number is considered a perfect square if it is a product of squaring a whole number (called integer). 0, 1, 2, 3, 4, 7, 8, and 9 are all whole numbers (same as integers). Numbers such as -8, 7.025, or 5 ½ are not whole numbers. Remember squaring is when a number is multiplied by itself. For example, 81 is a perfect square because it is a product of 92 which is the same as 9×9. Notice 9 is a whole number (integer).

In our example the square root of 21 is 4.5825756949558. Since 4.5825756949558 is not a whole number therefore 21 is not a perfect square.

ANSWER: 21 is not a whole number 

Is the square root of 21 rational or irrational number?

A number is rational when it can be made by dividing a whole number by a whole number. A whole number which is also called an integer does not have a fractional part itself. Simply said a number is rational if it can be written as a fraction. 

A quick method to determine if 21 is a perfect square. The square roots of perfect squares are all rational numbers. The square roots of numbers that are not a perfect square are all irrational numbers. Since we know that 21 is not a perfect square therefore 21 is not a rational number.

Principal square root of 21

Every positive number has two square roots. One of the square roots is positive and another one is negative. For example the square roots of 21 are -4.5825756949558 (negative) and +4.5825756949558 (positive) because  (-4.5825756949558)^2=(+4.5825756949558)^2=21. The positive square root is denoted as “the principal square root”. Typically, when we are calculating “the square root of a number” we mean the principal square root. In our case it is positive 4.5825756949558 or +4.5825756949558 which is written as 4.5825756949558. As you may know if there is no minus (-) sign before a number it is a positive number. 

Again the principal square root of 21 is 4.5825756949558.

Calculating the square root of 21 with a calculator

In order to calculate the square root of 21 with a basic or a scientific calculator you need to enter 21 and then press the key with this sign  “√x”

√21 = 4.5825756949558

Calculating the square root of 21 in Excel and Google Sheets

There are two functions you can use to do this calculation. You can use the function SQRT () to calculate the square root of any number in Excel and Google Sheets. Click on a cell and type =SQRT(21). Hit enter. You will get 4.5825756949558.

You can also use the POWER function which works like an exponent is an equation. To find a square root of 21 type =POWER (21, 1/2). Remember square roots can be expressed as exponents as we discussed earlier in this article.

Table: N^th roots of 21

In the section above we explained how the square root (which is the 2^nd root) of 21 is calculated. However there are more roots of 21. Find the N^th roots of 21 in the table below:

Table: Square root of numbers around 21

This table lists numbers around 21 and their respective square roots.

Table: Perfect square numbers

This table lists perfect square numbers from 1 through 10,000.

Visit squarerootof.net for any square root related calculations including square roots, negative square roots, square roots from fractions, exponentiation and other related calculations.