18
The number 18 has significance across various domains including mathematics, science, culture, and history:
-
Mathematics:
- 18 is an even number and a composite number, being the product of the first three prime numbers (2, 3, and 3).
- It is the only number that is twice the sum of its digits: 1 + 8 = 9, and 2 × 9 = 18.
- In the Pythagorean triples, (9, 12, 15) has 18 as the hypotenuse.
-
History and Culture:
- In Judaism, the number 18 is considered very lucky because the Hebrew word for life, "Chai" (חי), has a numerical value of 18 according to Gematria. Consequently, gifts or donations in multiples of 18 are common.
- The 18th Amendment to the United States Constitution was ratified in 1919, leading to the era of Prohibition.
- Age of majority in many countries is set at 18, marking the transition from adolescence to adulthood.
-
Science:
- The atomic number of Argon is 18.
- In chemistry, 18 electrons are considered a stable configuration for the outermost shell of atoms, leading to the concept of the Octet rule.
-
Sports:
Sources:
Related Topics: