+ 1 are prime, as well as the only prime number 
  
    
      
        p
      
    
    {\displaystyle p}
   such that 
  
    
      
        p
      
    
    {\displaystyle p}
   - 1 yields another prime number, 2. A triangle is made of three sides. It is the smallest non-self-intersecting polygon and the only polygon not to have proper diagonals. When doing quick estimates, 3 is a rough approximation of π, 3.1415..., and a very rough approximation of e, 2.71828...
3 is the first Mersenne prime, as well as the second Mersenne prime exponent and the second double Mersenne prime exponent, for 7 and 127, respectively. 3 is also the first of five known Fermat primes, which include 5, 17, 257, and 65537. It is the second Fibonacci prime (and the second Lucas prime), the second Sophie Germain prime, the third Harshad number in base 10, and the second factorial prime, as it is equal to 2! + 1. 3 is the second and only prime triangular number, and Gauss proved that every integer is the sum of at most 3 triangular numbers. 3 is the number of non-collinear points needed to determine a plane and a circle.
Society and culture
Economics
In 2015 it cost about US$14,100 per year. One article calculated this to be about $400,000 to $500,000 per quality-adjusted life year (QALY), which did not meet "generally accepted" cost-benefit thresholds. The authors calculated that an annual cost of $4,500 would meet an acceptable $100,000 per QALY standard. On October 26, 2018 the maker of the drug, Amgen, announced a 60% cut in price and the drug now costs $5,850 per year. References
External links
"Evolocumab". Drug Information Portal. U.S. National Library of Medicine.