He largest known composite Fermat Number was discovered this summer by Dr John Cosgrave of the Department of Mathematics, St Patrick's College, Drumcondra. This is a special number that is the product of two prime numbers, numbers that are divisible by one and themselves alone. Large prime numbers are of importance for encryption of electronic messages.
The most commonly used method to create secure e-mail is entirely dependent on prime numbers. The number is enormous almost beyond comprehension. If the number was written out on paper and the pages stacked, the stacks would cover so huge an area that the entire universe could fit into it with room to spare.
Dr Cosgrave will give a public lecture, "The History of Fermat numbers from August 1640", on Thursday at 8 p.m. in Room €201, St Patrick's College, Drumcondra. Also attending will be Yves Gallot, whose computer programme Dr Cosgrave used in his discovery. For further information contact his website: http:// www.spd.dcu.ie/johnbcos