How do you write $1.7 \times {10^7}$ as an ordinary number?

Hint: The expression that we need to write as an ordinary number is in the form of scientific notation. The scientific notation means expressing very large numbers and very small numbers in standard form.

Complete step-by-step solution:
The given expression is written in the scientific notation. Scientific notation is used to write very large numbers and very small numbers in standard form using the exponents.
Scientific notation is a kind of shorthand that can be used to write large or small numbers. We write the numbers in scientific notation as the product of two numbers.
Now, the given expression is $1.7 \times {10^7}$
Here, $\;1.7$ , is a number greater than or equal to but less than $10$ and the exponential number is in the power of $\;10$ .
Now, to simplify this expression further, first we expand the exponential number in the power of $\;10$ . Then the expression becomes
$= 1.7 \times 10000000$
Now, we operate multiplication and move the decimal point $7$ places to the right. Then we get
$= 17000000$ .

Hence, we can say that the scientific notation of the expression $1.7 \times {10^7} = 17000000$.

Note: In the scientific notation of a number, the exponent is positive for the larger number and the exponent is negative for the smaller number.
Using scientific notation, we can represent large numbers or small numbers in a simpler form. Huge numbers are difficult to be written on a piece of paper. By using the scientific notation, we can represent numbers in a multiplication of a single-digit number and $\;10$ raised to the power of the exponent.