How to round this one?

Question

I get a pretty big number from the api and pass it to the interface, how can I round it up to six decimal places?

if(key == 'hashrentReward')
        {
            spans = document.getElementById('hashrentReward').getElementsByTagName('span');
            console.log(spans[0].innerText);
            values[key] = values[key] * '864000';
                
        }