27661 is a semiprime whose average of its prime factors is a perfect power, here 169 = 13^2. The remaining such numbers up to 40000 are:

27661, 27887, 28073, 28247, 28417, 28967, 29047, 29135, 29431, 30237, 30311, 30461, 30847, 31597, 31681, 32047, 32551, 32567, 32847, 33431, 33527, 34207, 34241, 34647, 34951, 35249, 35333, 35741, 35807, 36077, 36391, 36737, 37327, 37437, 37733, 37777, 38081, 38191, 38407, 38551, 38687, 39421, 39449, 39665

27661 is a cyclic and Duffinian number.

27661, when viewed as a rectangle with sides 139 and 199, has the same perimeter as a square of side 169. However, the square has an area of 28561 square units whereas the rectangle has an area obviously of 27661 square units.

27661 can be rendered as a digit equation as follows:

2 - 7 ^ (6 - 6) = 1