HI Deborah,
One straightforward way would be: divide by 2. If that result is an integer, divide it by 3. If that result is an integer, divide it by 4 ... keep going until the division either returns 1 somewhere along the line, in which case the starting point was the factorial of the last-used integer, or does not return 1 and returns values less than 1, in which case the starting point was not the factorial of an integer. Programming that up should give you more good practice with Matlab.
If you go this direction you will of course have to check if a number is an integer. Matworks has an 'isinteger' function, but somewhat perversely it does not work for ordinary Matlab double precision numbers. But you can use
floor(n) == n
and if the result is true, n is an integer.
