7 is the natural number following 6 and preceding 8. It is an odd prime number. Its divisors are 1 and 7.
Binary representation of 7 is 1112.
There are seven days in a week.
There are 7 letters in TUESDAY, which is the only day of the week whose name contains a prime number of letters.
Seven is the only odd prime that becomes even by deleting a letter.
The Seven Bridges of Königsberg is a famous solved mathematics problem posed by Euler.
Graph theorists have been able to prove that 7 colours are required on a donut-shaped map to ensure that no adjacent areas are the same.
There are 7 indeterminate forms involving 0, 1, and infinity.
Double 7! to get the exact number of minutes in a week (i.e., 7 days).
In most Hindu marriages the bride follows the groom 7 times around the holy fire, which is called a Saptapadi.
The sum of seven consecutive primes beginning with 7 is seven times the seventh prime:
7 + 11 + 13 + 17 + 19 + 23 + 29 = 7 × 17.
7-segment display is commonly used in electronic display devices to form the digits 0 through 9.
In complex number theory, the 7th roots of unity are the complex solutions to the equation 𝑧7 = 1. These solutions lie on the unit circle in the complex plane and are spaced evenly around it, forming a geometric shape known as a regular heptagon.
There are 7 frieze groups in two dimensions, consisting of symmetries of the plane whose group of translations is isomorphic to the group of integers.
The numbers on opposite sides of a standard die always add up to 7. The opposite faces on a dice add up to 7, i.e., 6 + 1, 2 + 5 and 3 + 4.
If you roll a pair of dice, the most likely sum you will get is 7 (1, 6 or 6–1 or 2–5 or 5–2 or 3–4 or 4–3). So, the probability of getting 7 is 1/6.
The Millennium Prize Problems are seven problems in mathematics that were stated by the Clay Mathematics Institute in 2000. Currently, six of the problems remain unsolved.
In decimal representation, the reciprocal of 7 repeats six digits (as 0.142857), whose sum when cycling back to 1 is equal to 28.
The number 7 is the only prime followed by a cube minus one: 7 = 23 – 1.
We can write it as the difference of two squares: 7 = 42 – 32. Using prime numbers, we can represent it as: 7 = 25 – 52. Also, we can write it as 3 ∙ 5 – (3 + 5) = 7.
The cube of 7 has the following interesting representation: 73 = 343 = (3 + 4)³.
The number 7 is a centered hexagonal number, as you can see in the pattern above.
The number 7 is the smallest number of sides of a regular polygon that cannot be constructed with straightedge and compass alone.
There are 7 points and 7 lines in the smallest projective plane.
The seven seas mean all the oceans of the world.
There are seven colours in the spectrum of light: red, orange, yellow, green, blue, indigo, and violet.
