Ask HN: largest number you've had to store in an application?

Heh, I actually overran a signed integer 2 years ago in an app for a major financial company.

Yes, that's > $2,147,483,647

Thanks, subprime mortgage crisis!

Huge. Longer than 2^30 digits. I was working on statistics. Doing probabilities requires doing some crazy factorials. These often require handling large freaking numbers. I'm a PHP guy, so BC Math and GMP Math are my saviors in this area.

Thankfully, all the huge numbers are just in the computation of the statistics and don't need to be stored long term in a database. The thought of having to store an integer in a BLOB is frightening.

twitter id's is the first thing that comes to mind.

I used to work for an egg wholesaler. We paid the farmers by the egg according to grade. We accounted in eggs.

Do you know how many eggs are sold in the UK?

We had to write a special class to handle eggs because we blew the unsigned integer on a VAX.

If you want universal uniqueness you should be looking at 128-bits (http://en.wikipedia.org/wiki/Universally_Unique_Identifier)

You don't have much space left in 64 bits for some financial numbers. FX swap trades with a billion dollars on one side and some very devalued currency on the other (e.g. zimbabwe dollars 1:60,000,000 at one point).

It gets worse when you start adding those numbers up.

I built an aviation mapping engine that used fixed point math for lat/lon representation. It basically used an entire 32bit signed int and gave a guaranteed minimal resolution of 3 feet. It would quite often go to the ragged edge of what you can fit in a 32 bit quantity.

The fun bit was that you had to use 2 combined registers (ARM) to represent a 64bit quantity so you could do multiplication and keep all your precision.

Oh, for the luxury of a FPU...

public/private keys for RSA - 1024 bit numbers.

factorial(30..50) -- for factoradics (http://en.wikipedia.org/wiki/Factoradic). Representing the reproducable state of a list of randomly ordered items.

I implemented Tupper's Self-referential formula which depends on an extremely large number (although I suppose that's cheating a bit, the number is actually an encoding of a bitmap).

I've had to build a system to theoretically handle indexes up to 1.2553643905927429e+30 but we haven't got that far yet (biggest # is a billion billion billion or so)

1000000! took me about an hour to calculate on a supercomputer in 1988. It's roughly 5 million decimal digits.

I have worked on Financial Apps where we have ended up blowing away the 64-bit threshold.

I guess astronomical modeling uses ... astronomically big numbers?

EPC Gen2 RFID tags have a 96 bit unique id that we store

Do parts of RSA keys count?

8374874823748327491