"The draft revision of the US Federal digital signature
standard, Draft FIPS 186-3, requires that the RSA public
exponent e be an odd positive integer >= 65,537.
See Appendix B.3.1 Criteria for IFC Key Pairs on p. 61:
(b) The exponent e shall be an odd positive integer such that
65,537 <= e < 2**(nlen - 2*security_strength)
where nlen is the length of the modulus n in bits.