Yes, 257 is a rational number.
A rational number is defined as any number that can be expressed as the quotient or fraction of two integers, where the denominator is not zero. In the case of 257, it can be written as 257/1. This clearly shows that it can be expressed as the ratio of two integers (257 and 1).
Additionally, all whole numbers, including integers like 257, are considered rational numbers since they can always be expressed in the form of a fraction with a denominator of 1. Therefore, 257 fits the definition of a rational number perfectly.