How much HP does a Jirachi have at level 100?

Answer 1

If Jirachi has a Caractersitic that hinders HP growth per level (i.e. Highly Curious), defeats Pokemon that don't yield HP EV's* (i.e. Tailow), and doesn't have 31 IV's** for HP, then its HP at level 100 will be 310.

If Jirachi has a Characteristic that promotes HP growth per level (i. e. Often Dozes Off), defeats Pokemon that do yield HP EV's (i.e. Slakoth), and does have 31 IV's for HP, then its HP at level 100 will be 404.

*Each stat (i.e. HP) is allowed only a maximum of 255 Effort Value/(points)

**Each stat (i.e. HP) is allowed only a maximum of 31 Individual Values/(points) and these values are randomly generated when you encounter the Pokemon. There are IV calculators on several Pokemon fan-sites (