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 TOPICS This page:   prime numbers    Search    See also the Dr. Math FAQ:   prime numbers Internet Library:   prime numbers MIDDLE SCHOOL About Math Algebra    equations    factoring expressions    graphing equations Arithmetic    division    exponents    factorials    factoring numbers    fractions/percents    logarithms Definitions Geometry    2-dimensional      conic sections/        circles      triangles/polygons    3D and higher      polyhedra History/Biography Logic Measurement    calendars/      dates/time    temperature    terms/units Number Sense    factoring numbers    negative numbers    pi    prime numbers    square roots Probability Puzzles Ratio/Proportion Statistics Word Problems Browse Middle School Prime Numbers Stars indicate particularly interesting answers or good places to begin browsing. Selected answers to common questions:     Testing for primality. Prime Numbers [01/31/1997] What are the prime numbers and why are they prime numbers? Prime Numbers vs. Prime Factors [01/13/1997] What is the difference between a prime number and a prime factor? 1 and 0: Prime or Composite? [10/06/1997] Is the number one a prime or a composite number? Why? What about zero? 400-Digit Product of Two Primes [11/04/2002] What two prime numbers when multiplied together will equal a 400-digit number? Abundant and Deficient Numbers [10/14/1997] What are abundant and deficient numbers, and what are they used for? Adjacent Primes [11/26/2001] What are adjacent primes? Checking if a Number from 1-100 is Prime [09/06/2008] Is there an easy way to determine if a number between 1 and 100 is prime without having to do a lot of division? Classifying the Number One [11/27/1998] My students have learned about prime and composite numbers. What classification fits the number 1? Code with Only a String of 1's [10/28/2002] You need to send a numeric code to someone, such as one used to unlock a padlock. Determining if a Large Number is Prime [05/05/2004] Is 333667 a prime? I have ruled out all evens plus 5, 10, 7, 8, 9, 13, 17, and 19 as possible factors but do not know how to proceed from there. Determining If a Number is Prime [08/12/2004] Is there a formula for determining if a number is prime? Etymology of the Word Prime [08/28/2002] Why are prime numbers called prime? Euclid's Algorithm for Finding a GCD [10/12/2002] Find the only number besides one that is a common factor of 163231, 152057, and 135749. Factoring Very Large Numbers into Primes [12/05/2003] Is there a way to factor really big numbers into primes other than the usual method of dividing by successive primes? Factors and Multiples [01/27/1998] My son is in 4th grade and needs help naming a common multiple of a pair of numbers. Factors and Primes [09/10/1997] A prime number is a number greater than 1 and has only 2 divisors, 1 and itself. Without the stipulation greater than one, what would be the effect? Fastest Primality Test? [12/21/2005] I found an article on the Internet discussing a new test to determine if a given number is prime or composite. Is it the fastest test? Finding Prime Factors of Factorials [11/26/2004] How many factors of 2 are contained in 100! ? Finding Prime Numbers [12/5/1995] What is the easiest way to find a prime number? General Formula to Find Prime Numbers? [10/12/2005] I was wondering if it is possible that there exists a general formula to know what numbers are prime, or has it been proven that no such formula could exist? What evidence do we have for either case? How does the Sieve of Eratosthenes Work? [10/29/2002] How does the Sieve of Eratosthenes work for finding prime numbers? How Many Primes Are Known? [01/21/2003] How many prime numbers are currently known? The Importance of 1 Not Being a Prime Number [04/25/2009] Does division by zero make sense in a field of cardinality 1? If there is only one element, the multiplicative and additive identities must be the same, so 0 = 1 and 1/0 = 1/1 = 1. Is that true? Infinite Primes [12/4/1994] We would appreciate it if you could send us the largest prime to date, and how many digits it has. Is Zero Prime or Composite? [10/23/1995] Is zero prime, composite, or neither? Largest Prime Number [9/8/1996] What is the largest prime number yet found? Least Common Multiple, 2-10 [10/28/2002] Find the smallest counting number that is divisible by the numbers 2 through 10. No Largest Prime Number [8/19/1996] What's the largest prime number? (proof by contradiction). Numbers with Large Exponents [08/22/2001] How many zeros end the number 2^300 * 5^600 * 4^400? Perfect Numbers [08/14/1997] What is the highest perfect number that has been found? How many perfect numbers are there? What are they? Perfect Numbers - Basics, History [11/3/1996] What is the next perfect number after 28? Prime and Composite Numbers, Sieve of Eratosthenes [01/28/1997] I need a list of all prime numbers and all composite numbers up to 50. Prime and Consecutive Numbers [11/16/2001] Why are 3, 5, and 7 the only numbers that appear to be prime and consecutive? Prime, Composite, or Neither? [09/16/2003] What are prime and composite numbers? Prime Factors [01/28/2006] What is a number with only two prime factors and no repeated factors? Prime Number 2001, Sieve of Eratosthenes [01/25/1997] Is 2001 a prime number? Prime Numbers: 20-30 [01/31/1997] What are the prime numbers 20 through 30? Prime Numbers and the Sieve of Eratosthenes [10/20/2003] How can I figure out the last or largest prime number I need to use in the 'Sieve of Eratosthenes' in order to find all the primes between 1 and 500? Prime Numbers in Cryptography [08/14/1999] What are some practical uses of prime numbers? Prime Number Tests [11/12/1998] Is the number 55409243 prime? How can you test to see whether a number is prime? 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