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HP-UX 11i Version 3: February 2007

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factor, primes — factor a number, generate large primes


factor [number]

primes [start[stop]]


If no arguments are provided on the command line, factor waits for a number to be typed in. If a positive number is typed, it factors the number and print its prime factors; each one is printed the proper number of times. It then waits for another number. factor exits if it encounters a zero or any non-numeric character.

If an argument is provided on the command line, factor factors the number as above, then exits.

Maximum time to factor is proportional to sqrt(n) and occurs when n is prime or the square of a prime.

The largest number that can be dealt with by factor is 1.0e14.

primes prints prime numbers between a lower and upper bound. If no arguments are provided on the command line, primes waits for two numbers to be typed in. The first number is interpreted as the lower bound; the second as the upper bound. All prime numbers in the resulting inclusive range are printed.

If start is specified, all primes greater than or equal to start are printed. If both start and stop are given, all primes occurring in the inclusive range start through stop are printed.

start and stop values must be integers represented as long integers.

If the stop value is omitted in either case, primes runs either until overflow occurs or until it is stopped by typing the interrupt character.

The largest number that can be dealt with by primes is 2,147,483,647.


Both commands print Ouch when the input is out of range, illegal characters are encountered, or when start is greater than stop.


Print the prime factorization for the number 12:

factor 12

Print all prime numbers between 0 and 20:

primes 0 20

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