129

This number is a composite.

If you factor 129 into primes (3 * 43) and concatenate (343) you get a perfect prime cube (7³). Note that 129 is the smallest sum of distinct seventh powers (1⁷ + 2⁷). [Brueggeman]

129 is the sum of the first |1-2-9| primes. [Nilsson]

The smallest sum of the first n primes that is divisible by three (n=10). [Gaydos]