Free interactive math game: Prime Factorization — 60 = 2·2·3·5. Part of the Divisibility & Numbers category on MathKite.
Taken from the generator that powers this exercise. A fresh set appears every time the page is opened, and the printable worksheet holds ten of them.
Writing a number as a product of primes, which is its unique fingerprint.
Divide by the smallest prime that fits and keep going with the quotient until only primes remain.
12 divides by 2 to give 6, which divides by 2 to give 3, so 12 = 2 x 2 x 3.
Leaving a composite in the answer. Writing 12 as 2 x 6 is not finished, because 6 still breaks down.