Semiprimes (pq-numbers) guarantee that if p and q are prime numbers the only divisors of the result of
p*q are p and q.
My question is: Does this hold true for
p*q*r as well?
3*5*7=105. Are there any three numbers other than 3, 5 and 7 so that
Of course if there are non, the follow up question is, what about the other prime-multiplications like
I have this question because I came across an article about sending messages to space and the Arecibo message used a semiprime to transmit information about the layout of the message. If we could do the same with three numbers we could make a 3d layout.
The cardinality of 1,679 was chosen because it is a semiprime (the product of two prime numbers), to be arranged rectangularly as 73 rows by 23 columns. The alternative arrangement, 23 rows by 73 columns, produces jumbled nonsense (as do all other X/Y formats). The message forms the image shown on the right, or its inverse, when translated into graphics, characters and spaces.
from the Wikipedia page