27561 is a member of OEIS A361696: semiprimes of the form k^2 + 5, here k = 166. The sequence can be generated as follows (permalink):

INPUT

k=5

S=[n for n in [(k+1)..40000] if (len(divisors(n))==4 and len(prime_factors(n))==2) or is_square(n)==1]

L=[]

for s in S:

  if sqrt(s-k)==int(sqrt(s-k)):

    L.append(s)

print(L)

print(len(L))

OUTPUT

[6, 9, 14, 21, 69, 86, 201, 329, 446, 489, 581, 681, 734, 789, 905, 1094, 1769, 1941, 2606, 2921, 3254, 3369, 3849, 3974, 4101, 4629, 4766, 6729, 7061, 7401, 8105, 8654, 9609, 9806, 10409, 10821, 11669, 12326, 13929, 17429, 17961, 19049, 20741, 23109, 23721, 24341, 27561, 30281, 31334, 32405, 33494, 33861, 34601, 35349, 35726, 37641]

56

27561 is an Ulam, Duffinian and lucky number

27561 is a D-number because it divides all k^(n-2)-k for all 0<k<n where k is coprime to n.

27561 can be rendered as a digit equation as follows:

-2 + (7 - 5) | 6 = 1