This number is a prime.
The number in the street address of the Administrative building at Saint-Prime (599, rue Principale, Saint-Prime, Québec, Canada). [Blanchette]
The smallest prime whose digits form a triangle with the largest prime perimeter. [Loungrides]
The smallest prime that creates other primes when sandwiched between two-digit repdigits in three ways: (15991, 35993, 75997). [Loungrides]
The 599th beastly number is 220666. This is the smallest case in which the sum of digits of a beastly number (22) is less than the sum of digits of its beastly index (23). Is there any example in which sums of digits are equal? [Gaydos]
Historically, subprime (also referred to as "non-prime") borrowers were defined as having FICO scores of 599 and below.
The five prime months of the year contain 151 days. Note that 5 * 151 - (5 + 151) = 599, 5 * 151 + (5 + 151) = 911 and 911 - 599 +/- 1 are twin primes. [Homewood]