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7 (number) facts for kids

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−1 0 1 2 3 4 5 6 7 8 9
Cardinal seven
Ordinal 7th
Numeral system septenary
Factorization prime
Prime 4th
Divisors 1, 7
Greek numeral Ζ´
Roman numeral VII
Roman numeral (unicode) Ⅶ, ⅶ
Greek prefix hepta-/hept-
Latin prefix septua-
Binary 1112
Ternary 213
Senary 116
Octal 78
Duodecimal 712
Hexadecimal 716
Greek numeral Z, ζ
Arabic ٧,7
Persian ٧ - هفت
Chinese numeral 七(qi)
Devanāgarī (saat)
Hebrew ז (Zayin)

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


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,
  1. Take off the last digit and multiply it by 2.
  2. Subtract the root number from the product .
  3. Repeat the second step again and again until it is clearly that the number is divisible by 7 or not.



  1. 5×2=10, 91878-10=91868
  2. 8×2=16, 9186-16=9170
  3. 0×2=0, 917-0=917
  4. 7×2=14, 91-14=77

77 is divisible by 7, so the original number 918785 is also divisible by 7.

Proof: Pretend a is the root number and b is the last digit. Then 10a+b is the whole number. If the whole number (10a+b) is divisible by 7, 3a+b is also a multiple of 7. And (3a+b)-7b= 3a-6b also divide 7. That proves 3a-6b is divisible seven, since 3 and 6 are both multiples of 3. So a-2b 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 AL-HIJR 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)

See also

Kids robot.svg In Spanish: Siete para niños

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7 (number) Facts for Kids. Kiddle Encyclopedia.