23 (the 9th prime)

 
Next prime29
Previous prime19
Octal(27)8
Hexadecimal(17)16
Prime gap6
6th Sexy prime (the small number)The big number is 29 .
5th Prime of the Form 4n+3 
5th Factorial prime4! - 1
5th Sophie Germain prime 
4th Safe prime 
7th Left-truncatable prime 
5th Right-truncatable prime 
5th Two-sided prime