Prime numbers (or coprimes) have few well-known uses but interesting ones.
The classical example is that prime numbers are used in asymmetric (or public key) cryptography. Prime numbers and coprimes are also used in engineering to avoid resonance and to ensure equal wear of cog wheels (by ensuring that all cogs fit in all depressions of the other wheel).
Are there other known real-world, and especially physical world or engineering, applications for prime numbers?
Existing questions on the Mathematics stackexchange forum revolve mostly around computation examples (see for example Real-world applications of prime numbers?). These questions do not list physics or engineering real-world examples of prime numbers. They concentrate mostly on computational examples.