H.C.F. of two prime numbers is 1.
Product of numbers = (1 x 155) = 5*31
Let the numbers be a and b.
Then, ab = 155.
Now, co-primes with product 161 are (1, 155) and (5, 31).
Since p and q are prime numbers and p > q,
we have p = 31 and q = 5.
=> p – q = 31 - 5
= 26