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Comment by mixmax | Hacker News Reader

In my country social security numbers consist of two numbers, and mine consists of two twin primes. Probably the only one in the country.

This is something I can only brag about on HN :-)

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Finding mixmax's country of residence, social security number, name and address is left as an exercise for the reader :)

should definitely be doable - but using it to defraud me would be hard. Here social security numbers are used as an identifier, you can't really get to anything interesting with it. For that you'll need my passport, drivers license, digital ID or something similar. You can probably go to the doctor and claim to be me, but that's about it.

As a matter of fact a popular singer once published an album where the title was his social security number to show that you can't do much with it.

By my math, if you're talking about Denmark, I don't think you're as unique as you think you are. There are a total of about 18 million valid Danish ID numbers (approximately 36.5k valid DDMMYY combinations * approximately 500 valid serials that meet the checksum), of which 204,099 are two twin primes. So I'd expect about 1% of the country to have two twin primes for their ID number.

So not only are you probably not the only one in the country to have two twin primes for an ID number, you're probably not the only Dane on Hacker News for whom that's true!

As long as we are on the subject of primes, my parents telephone number is prime (and in Denmark telephone numbers are 8 digits).

WTF is the odds of that?

If my math is to be believed, 5096876/90000000 or ~0.056632; roughly 1 in 20.

Edit: Here's my program: http://pastebin.com/sBsXjPt5

Usage: gcc primes.c -O2 -o primes; ./primes 8 | wc -l

Edit 2: Nevermind; I'm dumb. First, there are 10^8 unique 8 digit combos, not 10^8-10^7. If all combinations were legal we'd have a probability of 0.05096876. But I assume all combinations are not legal, so that answer too is wrong. Maybe later if I'm bored and have more time I'll research the Danish telephone system and get an accurate number.

Alright - Denmark made it easy on me with the spreadsheet here: http://www.erhvervsstyrelsen.dk/numbering_lists

The probability that a valid, non-reserved, 8-digit danish phone number is prime is 4208056/73399100, or ~0.0573312. This probability does not account for number blocks which are valid but not yet assigned/purchased.

Code uses a copy of the number spreadsheet without header row saved as 'danish_numberlist.csv'

Code here: http://pastebin.com/kWUsHsL4

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