605

605 is a natural number that follows 604 and precedes 606. In mathematics, it has the prime factorization 5 × 11^2, making it a composite number. The sum of its digits is 11, and because 605 divided by 11 equals 55, it is a Harshad number in base 10.

In Roman numerals, 605 is written as DCV.

605 also designates real-world entities. In the United States, 605 is the area code for the entire state of South Dakota, one of the few states served by a single area code. Interstate 605 is a major freeway in the Los Angeles metropolitan area, functioning as an auxiliary Interstate that connects with I-5 and I-210 and is commonly referred to as the San Gabriel River Freeway.

Historically, 605 refers to the year 605 CE in the Gregorian calendar, placing it in the early seventh century. It can also denote 605 BCE in discussions of ancient history, depending on the era being referenced.