- 43 is an odd prime number.
- It is the smallest prime that is not a Chen prime.
- It is the fourth number of Sylvester's sequence.
- The first naturally occurring radioactive element is Technetium, with atomic number 43.
In Greek-based number-naming systems, 43 is associated with prefix "tritetraconta-", and with prefix "trequadraginti-" in Latin systems.
- Wolfram, Chen Prime