seventeen

Seventeen is the natural number that follows sixteen and precedes eighteen. It is a prime number, the seventh prime, and an odd number. In base-10 notation it is written as 17; its digits sum to 8. In Roman numerals it is XVII; in binary it is 10001 and in hexadecimal 11.

The word seventeen derives from Old English seofontīg, formed from seven and the suffix -tēne or -teen, which comes from ten. The combination reflects the historical pattern of forming numbers from seven or other units with the ten-based system.

In science, the atomic number 17 corresponds to chlorine, a halogen. Chlorine is a reactive nonmetal that occurs as a gas at room temperature and is essential in small amounts for biological processes. It is widely used in disinfection, water treatment, and the production of many consumer and industrial chemicals.

Culturally, 17 is sometimes regarded as unlucky in certain contexts. In Italian superstition, the arrangement of the Roman numerals XVII can be rearranged to VIXI, a Latin phrase meaning “I have lived,” which is associated with death. Conversely, some contexts celebrate 17 for its mathematical properties and its prominence in calendars and anniversaries.

Seventeen is also the name of a South Korean boy band formed by Pledis Entertainment in 2015. The group comprises 13 members divided into three units: hip-hop, vocal, and performance. They debuted with the mini-album 17 Carat and the single “Adore U,” and have since released multiple albums and tours.