Special properties of number 18 (Today’s Date)

1. 18 is a Heptagonal Number.
2. 18 is an Abundant Number. In number theory, an abundant number or excessive number is a number for which the sum of its proper divisors is greater than the number itself. The first few abundant numbers are 12, 18, 20, 24, 30, 36, ... There are only 21 abundant numbers less than 100, and they are all even. 
3. 18 is a Lucas Number (No. from the sequence 1, 3, 4, 7, 11, 18, 29, 47, 76, 123, … where first two numbers are fixed as 1 and 3, next number is the sum of its two preceding terms).
4. The 18 Regular Solids: the 5 Platonic Solid + the 13 Archimedean Solids.
5. 18 is the area and also the perimeter of a rectangle with 6 and 3-unit sides.
6. 18 is the only number that is twice the sum of its digits.
7. On Earth, the length of a day 900 million years ago was only about 18 hours.
8. There are 18 chapters in the Hindu epic tale Bhagavad Gita.
9. The Chemical Element Argon has an atomic number of 18.