MongoDB inserts float when trying to insert integer

db.data.update({'name': 'zero'}, {'$set': {'value': NumberInt(0)}})

You can also use NumberLong.

A slightly simpler syntax (in Robomongo at least) worked for me:

db.database.save({ Year : NumberInt(2015) });

If the value type is already double, then update the value with $set command can not change the value type double to int when using NumberInt() or NumberLong() function. So, to Change the value type, it must update the whole record.

var re = db.data.find({"name": "zero"})
re['value']=NumberInt(0)
db.data.update({"name": "zero"}, re)