What is the ruling on the fast of one who fasted the entire month of Ramadan without praying, and is he required to make up for that fast?

Neglecting prayer is a grave sin. The acceptance of a fasting person's fast who neglects prayer depends on the scholarly difference of opinion regarding their disbelief (kufr); whoever does not consider them a disbeliever deems their fast valid, and whoever considers them a disbeliever deems it invalid. The preponderant opinion is that it is obligatory to make up for missed prayers. Whoever knows their number should make them up. Whoever does not know their number should continue to make them up until they are reasonably certain that their obligation has been fulfilled.