5 (number)

5 (five /ˈfaɪv/) is a number, numeral, and glyph. It is the natural number following 4 and preceding 6.

In mathematics

Five is the third prime number. Because it can be written as 2²¹ + 1, five is classified as a Fermat prime; therefore a regular polygon with 5 sides (a regular pentagon) is constructible with compass and unmarked straightedge. 5 is the third Sophie Germain prime, the first safe prime, the third Catalan number, and the third Mersenne prime exponent. Five is the first Wilson prime and the third factorial prime, also an alternating factorial. Five is the first good prime. It is an Eisenstein prime with no imaginary part and real part of the form 3n − 1. It is also the only number that is part of more than one pair of twin primes. Five is a congruent number.

Five is conjectured to be the only odd untouchable number and if this is the case then five will be the only odd prime number that is not the base of an aliquot tree.

The number 5 is the fifth Fibonacci number, being 2 plus 3. 5 is also a Pell number and a Markov number, appearing in solutions to the Markov Diophantine equation: (1, 2, 5), (1, 5, 13), (2, 5, 29), (5, 13, 194), (5, 29, 433), ... ( A030452 lists Markov numbers that appear in solutions where one of the other two terms is 5). Whereas 5 is unique in the Fibonacci sequence, in the Perrin sequence 5 is both the fifth and sixth Perrin numbers.

No.5 (2PM album)

No.5 (stylized as №5) is the fifth Korean studio album (ninth overall) by South Korean boy band 2PM. The album was released in both physical and digital format on June 15, 2015, by JYP Entertainment.

Background and release

On May 8, 2015, JYP Entertainment announced that the group will be releasing their fifth album on June 1 and will be followed with two concerts to be held at Olympic Gymnastics Arena in Seoul, South Korea later that month. On May 11, 2015, the group's label explained that the album would be pushed backed to mid-June after video production company, Dextor Lab, pulled out of the production for the group's music video and would take legal action for the delay. On May 13, JYP said that they would be working with Naive Creative Productions for the music video. The album's tracklist was revealed on June 10, 2015. The album along with title track's music video was subsequently released on June 15, 2015 in South Korea.

Composition

The album's lead track, "My House", is a dance song and was written and composed by member Jun. K, who previously wrote and composed "Go Crazy" on their last Korean release. Other group members also participated in the production of the album.

No. 5 (Morning Musume album)

No. 5 (Number 5) is the fifth album from the J-pop idol group Morning Musume, released on March 26, 2003.

Overview

No. 5 is the last studio album to feature second generation member Kei Yasuda and first generation member Natsumi Abe as full members of the group. Yasuda graduated later in 2003, and Abe graduated in early 2004. It is also the first Morning Musume studio album to feature a former member as a returning guest artist, as Maki Goto guests on "Megami ~Mousse na Yasashisa~" and "Ganbacchae" (as well as appears on "Do It! Now", her last single as a member of the band).

Two of the songs, "Megami ~Mousse na Yasashisa~" and "Yes! Pocky Girls", are credited to two one-time Morning Musume spinoff groups, "Venus Mousse" and "Pocky Girls", respectively. The songs originated as promotional songs for Pocky biscuit snacks and appeared in versions that are least one minute shorter on the Petit Best 3 compilation album in December 2002. The first pressing came in special packaging with a photobook and a special mini poster.