The popularity is a boost to the Catholic Church which is reported to be struggling to recruit.
41 men in England and Wales began their training last year down - down from more than 150 in 1985.
Launching the app in January, the Catholic Church in England and Wales said the app aims "to help you go deep with God, and build solid ground with Him through prayer, through the lives of the Saints, and Scripture".
There are daily prayers and "questions to prompt reflection", such as "What is the Gospel saying?"
The app also has a diary so users can write down their answers and thoughts to these questions and track their "growth".
In mind of its target audience, it also has a link to the Twitter feed of the Pope and the latest Roman Catholic news, including a monthly quiz and a guide to new retreats or latest prayer festivals.
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