The first 65 digits of 6565 form a prime number. [Honaker]
The product of the first two primes of the form 4n + 1.
665 - 5 is the smallest prime of the form ac - b, where b = a - 1. Note that c is the concatenation of a and b. [Kulsha]
The smallest composite number of the form n2 + 1, where n is even.
65 is the ONLY number which gives a prime square, on adding as well as subtracting its reverse from it (65 + 56 = 112, 65 - 56 = 32). [Gupta]
The only number which is the difference of fourth powers of two primes. [Murthy]
(65!)2 + 1 is prime. [Dobb]
65 = 5 * 13 and (65) = (5) * (13) = 5 + 13. [Honaker]
(There is one curio for this number that has not yet been approved by an editor.)