Twenty-seven times over
صَلَاةُ الْجَمَاعَةِ تَفْضُلُ صَلَاةَ الْفَذِّ بِسَبْعٍ وَعِشْرِينَ دَرَجَةً
Salatu-l-jama'ati tafdulu salata-l-fadhdhi bi-sab'in wa 'ishrina darajah.
"Prayer in congregation is twenty-seven degrees better than prayer offered alone."
Narrated by Abdullah ibn Umar. Sahih al-Bukhari 645, Sahih Muslim 650
A short reflection
The same prayer and the same words, twenty-seven times the reward. When you can, pray with others: at the masjid, at work, at home with family.