Because a prime number has only the trivial factors 1 and , in his The Road Ahead , Bill Gates accidentally referred to a trivial operation when he stated "Because both the system's privacy and the security of digital money depend on encryption, a breakthrough in mathematics or computer science that defeats the cryptographic system could be a disaster. The obvious mathematical breakthrough would be the development of an easy way to factor large prime numbers [emphasis added]" (Gates 1995, p. 265).
Before one is admitted to a Master's program, one must have obtained a bachelor's degree in the same field of study at the same level. This means that someone with a HBO Bachelor's degree can normally not start directly with a WO Master, their scientific deficiencies are bridged in a half-year or full year program after which they can continue into the WO Master program. There might also be additional requirements such as a certain higher than average GPA, sometimes it's possible to complete the bridging program parallel to the HBO Bachelor. Note that completing this program does not grant the student a WO Bachelor's degree but merely entrance to the Master and that some two year WO Masters allow HBO Bachelor's degree holders in directly.