When is the reciprocal of a fraction a whole number? plz explain

The reciprocal of a fraction is only a whole number when
the numerator of the original fraction is ' 1 ' or a factor of
the denominator (original fraction is not in simplest form).

Any other time, the reciprocal of the fraction is another fraction.
(It'll be an improper fraction, and can be written as a mixed number.)

The reciprocal of a fraction is just the same fraction
turned upside down.

-- The reciprocal of  1/5  is  5/1  or just  5 .
   (Original numerator is ' 1 '.)

-- The reciprocal of  5/25  is  25/5  or just  5 .
    (Original fraction is not in simplest form.)

--  The reciprocal of  5/7  is  7/5 , or  1 and 2/5 .