7 (number)

natural number

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

← 6 7 8 →
-1 0 1 2 3 4 5 6 7 8 9
Cardinalseven
Ordinal7th
(seventh)
Numeral systemseptenary
Factorizationprime
Prime4th
Divisors1, 7
Greek numeralΖ´
Roman numeralVII
Roman numeral (unicode)Ⅶ, ⅶ
Greek prefixhepta-/hept-
Latin prefixseptua-
Binary1112
Ternary213
Quaternary134
Quinary125
Senary116
Octal78
Duodecimal712
Hexadecimal716
Vigesimal720
Base 36736
Greek numeralZ, ζ
Amharic
Arabic٧,7
Germanic Variant7
Persian٧ - هفت
Urdu
Bengali
Chinese numeral七(qi)
Devanāgarī (saat)
Telugu
Tamil
Hebrewז (Zayin)
Khmer
Thai
Pronunciation of the number 7

Mathematics

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In mathematics, the number seven is an odd number and a prime number. It is also a Mersenne prime.

Divisibility Rule

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  • To test if an integer is divisible by 7 or not,
  1. Take off the last digit and multiply it by 2.
  2. Subtract that product from the root number (the integer without the last digit).[1]
  3. Repeat the second step again and again until it is clear that the number is divisible by 7 or not.

Example

918785

  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   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

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  • There are seven colors 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.
  • Seven gates of heaven (QUR'AN 15th chapter AL-HIJR verse 44)915:44).
  • Seven days in a week.
  • Seven seas and seven continents.
  • Cristiano Ronaldo wears the number 7, widely known as CR7.
  • The number 7 is often considered as luck in Western culture.

References

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  1. Divisibility rule by 7accessed 21 October 2016