Yes, it’s true.
The largest known prime number, found by the GIMPS project in August 2008, is this number here. (Warning: the number is very long, and the page loading might cause your computer to freeze temporarily).
In mathematical shorthand, the number can be written as
It took some time to familiarize myself with the seemingly endless digits, but now I’m confident that I can recite, without error, forward and backward, all of the digits of this number…
…in binary. 😛