801

801 may refer to several different things, including a number, a year, a telephone area code, and a computing architecture.

In mathematics, 801 is an odd composite number, with prime factorization 3^2 × 89. It is divisible by the sum of its digits (8+0+1=9), making it a Harshad number in base 10. In common representations, 801 is written in binary as 1100100001 and in hexadecimal as 0x321; in Roman numerals it is DCCCI.

Historically, the year 801 CE falls in the early Middle Ages. Charlemagne was the emperor of the Frankish realm at the time, and the Carolingian Empire was consolidating its influence across Western Europe.

Geographically, 801 is an area code in the North American Numbering Plan. It originally covered northern Utah, including Salt Lake City, and is currently overlaid by 385. The code is used for telephone numbers in that region.

In computing, IBM 801 refers to a research computer architecture developed by IBM that influenced later reduced instruction set computing designs.