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posted by Fnord666 on Monday November 05 2018, @02:29PM   Printer-friendly
from the it-means-it's-composite dept.

Submitted via IRC for Bytram

What Is an "Almost Prime" Number?

When I saw a math paper with the phrase "almost prime" in the title, I thought it sounded pretty funny. It reminded me of the joke about how you can't be a little bit pregnant. On further thought, though, it seems like someone whose pregnancy is 6 weeks along and who hasn't yet noticed a missed period is meaningfully less pregnant that someone rounding the bend at 39 weeks who can balance a dinner plate on their belly. Perhaps "almost prime" could make sense too.

A number is prime if its only factors are 1 and itself. By convention, the number 1 is not considered to be prime, so the primes start 2, 3, 5, 7, 11, and so on. Hence, a prime number has one prime factor. A number with two prime factors, like 4 (where the two factors are both 2) or 6 (2×3) is definitely less prime than a prime number, but it kind of seems more prime than 8 or 30, both of which have three prime factors (2×2×2 and 2×3×5, respectively). The notion of almost primes is a way of quantifying how close a number is to being prime.


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  • (Score: 2) by Pino P on Monday November 05 2018, @05:59PM

    by Pino P (4721) on Monday November 05 2018, @05:59PM (#758084) Journal

    0 people growing inside a fertile woman: Not pregnant
    1 person growing inside a fertile woman: Pregnant
    2 people growing inside a fertile woman: More pregnant, in this case with twins

    Starting Score:    1  point
    Karma-Bonus Modifier   +1  

    Total Score:   2