Coding standard for parsing primitive types in iOS

What is the best practice for parsing primitive type in iOS (int, float, BOOL etc.) while storing them in dataObjects for later use.

Should i parse it and store it as a NSNumber, or just store it as a primitive type property?

For example: if i'm getting 'userId' from server as long type. Should this be:

@property (nonatomic, strong) NSNumber *userId;

self.userId = [element objectForKey:@"user_id"];

or:

@property (nonatomic, assign) long userId;

self.userId = [[element objectForKey:@"user_id"] longValue];

Thanks.