19 (nineteen) is the natural number following 18 and preceding 20. It is a prime number.

In English speech, the numbers 19 and 90 are often confused, as sounding very similar. When carefully enunciated, they differ in which syllable is stressed: 19 /naɪnˈtiːn/ vs 90 /ˈnaɪnti/. However, in dates such as 1999, and when contrasting numbers in the teens and when counting, such as 17, 18, 19, the stress shifts to the first syllable: 19 /ˈnaɪntiːn/.

19 is the 8th smallest prime number. The sequence continues 23, 29, 31, 37...

19 is the seventh Mersenne prime exponent.

19 is the aliquot sum of two odd discrete semiprimes, 65 and 77 and is the base of the 19-aliquot tree.

19 is a centered triangular number, centered hexagonal number and a Heegner number.

You can make the number 19 by adding or subtracting but not multiplying (whole numbers), 19 can also be made by division.

The only non-trivial normal magic hexagon contains 19 hexagons (the other being 1).

19 is the first number with more than one digit that can be written from base 2 to base 19 using only the digits 0 to 9; the other number is 20.

Tegan and Sara are a Canadian indie band formed in 1995 in Calgary. Composed of identical twin sisters Tegan Rain Quin and Sara Keirsten Quin (born September 19, 1980). Both Tegan and Sara play guitar and keyboard and write their songs.

Tegan and Sara Quin were born September 19, 1980 in Calgary, Alberta. They began playing guitar and writing songs at age 15. They initially played as Plunk without a drummer or bass player. In 1997, they used their school’s recording studio to record two demo albums: Who's in Your Band? and Play Day. In 1998, they won Calgary's Garage Warz competition, using the studio time they won to record their first professional demo, Yellow tape, which was followed by Orange tape and Red tape.

Two songs from Red tape appeared on their first album, Under Feet Like Ours, which they released independently in 1999 under the name "Sara and Tegan". They later changed their name to "Tegan and Sara" because it was easier to pronounce and reprinted the album using that name. They also wanted their name to stand out amongst the other 'Sara' musicians at the time such as Sarah McLachlan and Sarah Slean. Tegan was easier to remember.^{[citation needed]}Neil Young's manager signed them to Young's Vapor Records label, and they released This Business of Art through Vapor in 2000. They have toured extensively since then.