Erroneous article at Business Insider

[cdnbcguy]

Where does '64 bits' come from?

http://www.businessinsider.com/how-to-mine-bitcoins-2013-3?op=1

[misterbigg]

64 digits. I the he's referring to the base-58-safe encoding (or whatever it's called)

[mestar]

Well, the 256 bit hash can be displayed as a 64 digit octal number.

But the author probably didn't think about that.  He's probably just confused about what miners are calculating, he thought that miners are looking for private keys,  or that Bitcoins are actually 64 bit integers and those you can too display as 64 digit binary numbers.

Not that it's of any importance what he was confused about.