Divisibility Tests

Computer Security

As mentioned in previous sessions, computer security depends on large values being difficult to factor. So, people who are trying to break encryption codes would like efficient methods for determining factors of large numbers. Such methods are only available for special cases.

In this session, we consider some basic special cases for determining whether a value is a factor of another value. For example, when simplifying fractions we would like to quickly determine whether a value is a factor of both the numerator and the denominator. How can we quickly determine whether a number is a factor of another number?

Try this problem. Which of the numbers below that are factors of 123,456?

2      3      4      5      6      9      10

return to top | next page