How to convert and compare NSNumber to BOOL?

First I convert BOOL value to NSNumber in order to put it into NSUserDefaults. Later I would like to retrieve the BOOL value from the NSUserDefaults, but obviously I get NSNumber instead of BOOL. My questions are?

1. how to convert back from NSNumber to BOOL?
2. How to compare NSNumber to BOOL value.

Currently I have:

if (someNSNumberValue == [NSNumber numberWithBool:NO]) {
    do something
}

any better way to to the comparison?

Thanks!