419
This number is a prime.
 
The Nigerian Advance Fee Scheme (also known internationally as "4-1-9" fraud after the section of the Nigerian penal code which addresses fraud schemes) is generally targeted at small and medium sized businesses, as well as charities.  [Croll]
 
Dutch microscopy pioneer and naturalist Anton van Leeuwenhoek (1632-1723) ground a total of 419 lenses during his life.  [Oakes]
 
419 is the smallest number which when divided by 2, 3, 4,
5, 6 and 7 leaves remainders of 1, 2, 3, 4, 5 and 6
respectively. It is also interesting to note that 419 is
one less than the least common multiple of the first 7
integers.  [Tryczak]
 
419 is a Sophie Germain prime, since 2 * 419 + 1 =
839, which is prime. Note that it is the 22nd Sophie
Germain prime, and 22 = 2 * 11 is the product of two
Sophie Germain primes.  [Carmichael]
 
419, 41, and 19 are all primes. The reversals of 419, 41, and
19 are all semiprimes.  [Poo Sung]
 
Milligrams of potassium in one-half cup cooked spinach.  [Karcher]
 
(419*22n + 1)/3 can never be prime.  [Wesolowski]
 
The position of the largest term ("mille") in a dictionary that lists the first thousand numbers alphabetically in
French.  [Beedassy]
 
Big Bertha was a 419 mm howitzer used by Germany in the
first world war. 
 
Largest n up to which Eulers famous polynomial n^2+n+41
generates primes or semiprimes only.  [Gupta]
 
419 West is a traditional American restaurant in Roanoke,
Virginia. 
 
In China, the number “419” is a codeword for “one night stand” because it's an approximate homonym for “for one
night.” 
 
The 419th decade is the first that has exactly three
brilliant years (4183, 4187, and 4189).  [Gaydos]
 
A jury in Virginia recommended that neo-Nazi James Alex Fields Jr., be given a sentence of life in prison plus an additional 419 years. 
 
419 Holistics is an Atlanta based company that strives to
be the premier hemp/cannabis company in the south.  [Buskey]
 
The smallest prime number for which the concatenation of the numbers in its Collatz Sequence is a prime.  [Gaydos]
 
The beginning of four consecutive prime numbers that contain two pairs of twins: {419, 421} and {431, 433}.  [Bergot]