7 (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 → ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	seven
Ordinal	7th (seventh)
Factorization	prime
Prime	4th
Divisors	1, 7
Roman numeral	VII
Roman numeral (unicode)	Ⅶ, ⅶ
Greek prefix	hepta-/hept-
Latin prefix	septua-
Binary	1112
Ternary	213
Quaternary	134
Quinary	125
Senary	116
Octal	78
Duodecimal	712
Hexadecimal	716
Vigesimal	720
Base 36	736
Greek numeral	Z, ζ
Amharic	፯
Arabic	٧,7
Germanic Variant	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

Pronunciation of the number 7

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,

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).
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 [math]\displaystyle{ a }[/math] is the root number and [math]\displaystyle{ b }[/math] is the last digit. Then [math]\displaystyle{ 10a+b }[/math] is the whole number. If the whole number ([math]\displaystyle{ 10a+b }[/math]) is divisible by 7, [math]\displaystyle{ 3a+b }[/math] is also a multiple of 7. And [math]\displaystyle{ (3a+b)-7b= 3a-6b }[/math] is also a multiple 7. That proves [math]\displaystyle{ 3a-6b }[/math] is divisible by seven, since 3 and 6 are both multiples of 3. So [math]\displaystyle{ a-2b }[/math] 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.
• Cristiano Ronaldo wears the number 7, widely known as CR7

7 (number) Media

• 

  Digtail Display with different 7ens

• 

  sevens

• 

  Numerals 078 shown in text figures, to illustrate descender on 7.

• 

  A hand written seven with a slash through it. The 7 was Kozuka Mincho Pro B font, the slash through the numeral was drawn in Paint

• 

  Graph of the probability distribution of the sum of two six-sided dice

• 

  His Master's Voice (small)

• 

  Shichifukujin