Furthermore , 3,203,431,780,337 was proven to be prime in 1867 .
In fact a larger prime was discovered in 1855 by Thomas Clausen ( 67,280,421,310,721 ) , though a proof was not provided .
3,203,431,780,337 was proven to be prime in 1867 .
In fact a larger prime was discovered in 1855 by Thomas Clausen ( 67,280,421,310,721 ) , though a proof was not provided .