5: Blown apart
Title text: Blown into prime factors
An anthropomorphic black number 70 sees a package, but it is a bomb that explodes when opened. This blows the number 70 into pieces, but what is left is not as could have been expected the number 7 and the number 0! The number 7 is there but instead of the number 0 there are the number 2 and the number 5.
The title text explains that the number has been Blown into prime factors, which for 70 are 2, 5 and 7. Prime numbers are numbers which can not be divided by any number other than itself and 1. Factors of a number are numbers which can be multiplied together to produce that number (and 2*5*7 = 70). 70 has other factors, including 1, 10, 14, 35 and 70, but 2, 5 and 7 are the only factors which are prime. All other factors of 70 (other than 1) can be formed by multiplying two (or three for 70 itself) of the prime factors together.
The colors of the numbers also seems to have been blown apart. In the subtractive color model the three primary colors are cyan, magenta and yellow, but when they mix two and two they form red, green and blue. Those are the three colors of the prime factors. When all three primary colors (and thus also when all three combination colors) are mixed the result is black as are the original 70 (according to the official transcript, although it looks dark blue in the drawing).
- [A black number 70 sees a red package and a line indicate that the number speaks. This small panel is partly overlaid on the next larger panel, which is shifted down.]
- 70: hey, a package!
- [The package explodes in a brown cloud of brown smoke. This panel is both behind the first in the top left corner, and below the last panel which has been laid on top of that corner:]
- [There are a red 7, a green 5 and a blue 2 lying near a scorched mark on the floor.]
- This comic was posted on xkcd when the web site opened on Sunday the 1st of January 2006.
- It was posted along with the 41 comics posted before that on LiveJournal.
- On the site, it is the first comic with an actual punchline (all previous comics are either just sketches or establishing the background for later comics)
- But this comic, as well as 12: Poisson also released that day, were never posted on LiveJournal.
- The release date is given from - wayback.archive. At least the 25th of October was the first crawl date.
- This also explains why it was "released" on a Tuesday.
- On xkcd it was released for the first time to the public on Sunday the 1st of January 2006.
- One of the original drawings drawn on checkered paper.
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