Re: 'can a negative number be a prime number?please give reason

Hello, Ahmad.  No, a negative number cannot meet the definition of a prime 
number. The definition of a prime number is "a positive integer that is not 
divisible without a remainder  by any integer except itself and 1" (Random House 
Webster's Dictionary).

Leaving off the requirement that it be a positive integer, the latter part of 
this definition also excludes negative numbers. Any negative number is divisible 
without remainder by at least 3 integers:  itself, 1, and -1.  

You can learn more about prime numbers here:
http://www.utm.edu/research/primes/