Yes, 4 is a rational number. A rational number is defined as any number that can be expressed as the quotient or fraction p/q of two integers, where p is the numerator and q is the non-zero denominator.
In the case of 4, it can be expressed as 4/1, where 4 is the numerator and 1 is the denominator. Since both 4 and 1 are integers and the denominator is not zero, 4 satisfies the definition of a rational number.
Therefore, 4 is indeed a rational number.