21 (number)

21 (twenty-one) is the natural number following 20 and preceding 22.

In mathematics

21 is:

21 has an aliquot sum of 11 though it is the second composite number found in the 11-aliquot tree with the abundant square prime 18 being the first such member. Twenty-one is the first number to be the aliquot sum of three numbers 18, 51, 91.

21st century

The 21st century is the current century of the Anno Domini era or the Common Era, in accordance with the Gregorian calendar. It began on January 1, 2001, and will end on December 31, 2100. It is the first century of the 3rd millennium. It is distinct from the century known as the 2000s, which began on January 1, 2000 and will end on December 31, 2099.

Transitions and changes

The first years of the 21st century have thus far been marked by the rise of a global economy and Third World consumerism, mistrust in government, deepening global concern over terrorism and an increase in the power of private enterprise. The longterm effects of increased globalization are not known, but there are many who are concerned about its implications. The Arab Spring of the early 2010s led to mixed outcomes in the Arab world. The Digital Revolution which began around the 1980s also continues into the present. The Millennials (born c. 1981-2000) having been born before the turn of the century give way to the rise of Generation Y & Generation Z in Western countries.

21st Century Girls

21st Century Girls is a teenage all-girl band founded in 1996 in Dudley, West Midlands, UK. Previously called She Devil, the band originally consisted of singer Leanne Garner, her sister Fiona Garner on bass, guitarists Kate Turley and Meriam "Mim" Mohammad, and drummer Charlotte Fendick. Fendwick later left the band, and Mohammad moved onto drums. In 1999, the band (then aged 14–16 years) were the first signing to Simon Fuller's 19 Recordings. After a major publicity campaign, the band released their debut single, "21st Century Girls", in June 1999. The single reached number 16 on the UK charts.

The band disbanded after they were dropped by their record company in 2000.

Kate Turley went on to form the band The Fight.

Discography

Album

1999 – "21st Century Girls" (19 Recordings/EMI #TOCP-65288) [Japan only release]

Singles

1999 – "21st Century Girls" / "If You're Mad Enough" (19 Recordings/EMI #TOCP-40121) UK No. 16

1999 – "Teenage Attack" / "Cats & Dogs" (19 Recordings/EMI #TOCP-40125) [Japan only release]

BTS

BTS may refer to:

Education

Media

Medicine

Technology

Century

A century (from the Latin centum, meaning one hundred; abbreviated c.) is 100 years. Centuries are numbered ordinally in English and many other languages (e.g. "the 7th century AD/CE"). A centenary is a hundredth anniversary or a celebration of this, typically remembrance of an event which took place a hundred years earlier; and its adjectival form is centennial.

Start and end in the Gregorian Calendar

According to the Gregorian calendar, the 1st century AD/CE started on January 1, 1, and ended on December 31, 100. The 2nd century started at year 101, the 3rd at 201, etc. The n-th century started/will start on the year (100 × n) − 99 and ends in 100 × n. A century will only include one year, the centennial year, that starts with the century's number (e.g. 1900 is the final year in the 19th century).

1st century BCE and AD

There is no "zeroth century" in between the 1st century BCE and the 1st century AD. Also, there is no year 0 AD. The Julian calendar "jumps" from 1 BCE to 1 AD. The first century BCE includes the years 100 BCE to 1 BCE. Other centuries BCE follow the same pattern.