No, \(1 \frac{3}{7}\) (which is a mixed number) is not an irrational number. It can be converted to an improper fraction:
\[ 1 \frac{3}{7} = \frac{7 \times 1 + 3}{7} = \frac{10}{7}. \]
Since it can be expressed as a fraction of two integers (where the denominator is not zero), it is classified as a rational number, not an irrational number. Rational numbers can be expressed as the quotient of two integers, while irrational numbers cannot be expressed in that form.