7 (number)

The number seven is a natural number that comes after six, before eight. In Roman numerals, it is VII.

 Mathematics 
In mathematics, the number seven is an odd number and a prime number.
It is also a Mersenne prime.
Divisibility Rule
 To test if an integer is divisible by 7 or not,
 Take off the last digit and multiply it by 2. 
 Subtract that product from the root number (the integer without the last digit).Divisibility rule by 7accessed 21 October 2016 
 Repeat the second step again and again until it is clear that the number is divisible by 7 or not.
Example

918785
 5×2=10, 91878-10=91868
 8×2=16, 9186-16=9170
 0×2=0, 917-0=917
 7×2=14, 91-14=77
77 is divisible by 7, so the original number 918785 is also divisible by 7.

Proof:
Pretend  is the root number and  is the last digit. Then  is the whole number.
If the whole number () is divisible by 7,  is also a multiple of 7. And  is also a multiple 7. That proves  is divisible by seven, since 3 and 6 are both multiples of 3. So  is also divisible by 7.

In the world
There are seven colours in the rainbow.
The atomic number of nitrogen.
The number of horizontal rows of elements in the periodic table.
The seven sacraments of the Catholic church.
The number of completion and fullness (HOLY BIBLE - Genesis 1; 2:1-2 - God is described to have created the Heavens and the Earth in six days, and rested on the seventh).
Seven gates of heaven (QUR'AN - 15th chapter AL-HIJR verse 44)915:44).
Seven days in a week.
Seven seas and seven continents.
The Wonders of the World (seven each in different segments of our world, such as cities, nature, underwater, and space)
Portuguese football player Cristiano Ronaldo wears the number 7, widely known as CR7.
“007”, is the codename for James Bond, a fictional MI6 spy (the “00” prefix signifying a “license to kill” and the “7” identifying Bond as the seventh agent in the 00 section of MI6).
The seven dwarfs in Walt Disney’s ‘Snow White and the Seven Dwarfs’ (1937).
The number 7 is often considered as luck in Western culture.

 References 

Category:Integers
Category:Prime numbers