|Roman numeral (unicode)||Ⅶ, ⅶ|
|Greek numeral||Z, ζ|
|Persian||٧ - هفت|
- 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.
- 5×2=10, 91878-10=91868
- 8×2=16, 9186-16=9170
- 0×2=2, 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. 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 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)
7 (number) Facts for Kids. Kiddle Encyclopedia.