773 is a prime number.
773 has a representation as a sum of two squares: 773 = 172 + 222.
773 is the hypotenuse of a primitive Pythagorean triple: 7732 = 1952 + 7482.
773 is the largest three-digit unholey prime; its digits have no holes.
773 is the smallest prime such that adding a preceding or trailing digit will always result in a composite if we omit the case where the leading digit is zero.
773 is a telephone area code for Chicago.Source: Prime Curios!
