Yes all natural numbers can be written as improper fractions.
For example, 4 = 8/2.
An improper fraction is when the numerator is larger than the denominator.
Although we could write 4 as 8/2, it's often best to reduce as much as possible.
When people typically think of improper fractions, it's when they reduced as much as possible and still have a fraction at the end.
For example: 8/6 = 4/3.