PRIME & COMPOSITE NUMBERS

PRIME NUMBER: A positive integer greater than "1" that can only be divided exactly (that is, without a remainder) by itself and 1.

COMPOSITE NUMBER: A positive integer greater than "1" that can be divided exactly by some other integer other than itself and 1.

FACTOR of an INTEGER: A whole number that can divide exactly into that integer.

The following exercise checks your ability to determine whether the first 50 integers are PRIME or COMPOSITE. (Works best on HTML version 4.0 or later.)

Click to
Is your choice or COMPOSITE?
If COMPOSITE, enter a FACTOR and .

Historical Note:
In 1742, Prussian historian and mathematician Christian Golbach conjectured that every interger greater than 5 could be written as the sum of three prime numbers, such as 21=11+7+3. ... As re-expressed by Swiss mathematician Leonard Euler, an equivalent conjecture (called the "strong" Goldbuch conjecture) asserts that all positive numbers greater than 2 can be expressed as the sum of two prime numbers.

[excerpted from The Math Book by Clifford A. Pickford, p. 178.]