All content from Kiddle encyclopedia articles (including the article images and facts) can be freely used under AttributionShareAlike license, unless stated otherwise. Cite this article:
7 (number) Facts for Kids. Kiddle Encyclopedia.



Cardinal  seven  
Ordinal  7th (seventh) 

Numeral system  septenary  
Factorization  prime  
Prime  4th  
Divisors  1, 7  
Roman numeral  VII  
Roman numeral (unicode)  Ⅶ, ⅶ  
Greek prefix  hepta/hept  
Latin prefix  septua  
Binary  111_{2}  
Ternary  21_{3}  
Quaternary  13_{4}  
Quinary  12_{5}  
Senary  11_{6}  
Octal  7_{8}  
Duodecimal  7_{12}  
Hexadecimal  7_{16}  
Vigesimal  7_{20}  
Base 36  7_{36}  
Greek numeral  Z, ζ  
Amharic  ፯  
Arabic  ٧,7  
Persian  ٧  هفت  
Urdu  
Bengali  ৭  
Chinese numeral  七(qi)  
Devanāgarī  ७ (saat)  
Telugu  ౭  
Tamil  ௭  
Hebrew  ז (Zayin)  
Khmer  ៧  
Thai  ๗ 
The number seven is a natural number that comes after six and 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 the root number from the product .
 Repeat the second step again and again until it is clearly that the number is divisible by 7 or not.
Example
918785
 5×2=10, 9187810=91868
 8×2=16, 918616=9170
 0×2=2, 9170=917
 7×2=14, 9114=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. So is the whole number. If the whole number ()is divisible by 7, that means is also a multiple of 7. And must also divide 7. is always divisible by 3, since 3 and 6 are all multiples of 3, through 3 is coprime to 7, and the last, is also divisible by 7.
In the world
 There are seven colors in the rainbow.
 The atomic number of nitrogen.
 The number of horizontal rows of elements in the periodic table.
 Seven gates of heaven (QUR'AN 15th chapter ALHIJR verse 44)915:44)
 Seven days in a week
 Seven seas and seven continents.
 Seven major parts of the human body (2 legs, 2 hands, trunk, neck and head)