Triple seven is today.

What myth behind this seven? In Wiki's page, you'll find some info about this seven. Something like this:

Seven in Mathematics:

- Seven is the 4th prime number.
- Seven is a Mersenne prime, since 2
^{3}- 1 = 7. - Seven is the fourth Mersenne prime exponent.
- Seven is the first Newman-Shanks-Williams prime.
- Seven is the third Lucas prime.
- Seven is the first Woodall prime.
- Seven is the second lucky prime.
- Seven is the second safe prime.
- Seven is the fourth factorial prime
- Seven is both a Carol number and a Kynea number.
- Seven is the smallest number that can't be represented as a sum of fewer than four non-zero squares.
- Seven is the fourth self number.
- Seven is the smallest happy number, except for the trivial example of 1.

- 999,999 divided by 7 is exactly 142,857. Therefore, when a vulgar fraction with 7 in the denominator is converted to a decimal expansion, the result has the same six-digit repeating sequence after the decimal point, but the sequence can start with any of those six digits. For example, 1/7 = 0.142 857 142.... and 2/7 = 0.285 714 285...
- A seven-sided polygon is a heptagon. The regular
*n*-gons for*n*≤ 6 can be constructed by compass and straightedge alone, but the regular heptagon cannot. Figurate numbers representing heptagons (including seven) are called heptagonal numbers. Seven is also a centered hexagonal number. - There are seven frieze groups, the groups consisting of symmetries of the plane whose group of translations is isomorphic to the group of integers.
- A group or a series of seven is a heptad.
- 7 is the only dimension, besides the familiar 3, in which a vector cross product can be defined.

Another myth, is around health issues. There's Seven Deadly Myths that you should read. It's explain some myths according people's heart health. One of the myth says

**"**Damage to heart tissue caused by a heart attack can be reversed by diet and exercise. While exercise and diet are essential elements in helping prevent a second heart attack, heart tissue damage caused by a heart attack is permanent and,at this point in time, cannot be reversed".

The most important thing that you must keep in mind, that

**7**(

**seven**) is the natural number following 6 and preceding 8.