7

7 (seven) is a positive integer following 6 and preceding 8. Its ordinal form is written "7th" or "seventh".
== Properties ==
*7 is an . 
*7 is a .
*It is a Mersenne prime, since it is equal to 23-1.
*It is the only prime number preceding a cube.
*It's Roman Numeral is VII. 
*It is associated with good luck in Western culture.
*It is the third number in Sylvester's sequence.
* All Fermat numbers larger than 5 end in 7.
==In googology==
In googology of 7.
*Some googologisms based on 7 are googolseptiplex, supersept and trisept. 
*In Greek-based number naming systems, 7 is associated with prefix hepta-, and with prefix septi- in Latin systems.
*Using the gag prefix, seven can be called gagtwo, since A(2,2) = 7.
* 7 is the last digit of Graham's number, and in fact it is the last digit of any power tower of 3's where the height of the tower is at least 2.
==In culture==
*There are 7 days in a week.Britannica, Week 
*The New Jersey metal band composed and performed the song "Seven" as part of their album .
*7 is a song made by Prince & The New Power Generation.
==Sources==
==See also==
cs:7
es:7
Category:Numbers
Category:Class 1
Category:Numbers 0-99
Category:Numbers with 1 to 2 digits
Category:Palindromic prime numbers
 
Category:Prime numbers
Category:Gag-