The The Chaplet of Divine Mercy is both a mental prayer and a vocal prayer.  It is a mental prayer when we meditate on the Mercy of Our Lord.  The vocal prayers are the Creed. the Our Father, and other prayers we articulate.

The Chaplet of Divine Mercy always begins with the Sign of the Cross. The Our Father and the Hail Mary follows. The Creed is prayed next. A recitation For the sake of His sorrowful Passion, have mercy on us and on the whole world is recited fifty times. Before every ten recitations, the formula Eternal Father, I offer You the Body and Blood, Soul and Divinity of Your dearly beloved Son, Our Lord Jesus Christ, in atonement for our sins and those of the whole world. is prayed. The last set of 10 recitations is followed by proclaiming God's Holyness, Mightiness and Imortalirty and then imploring his Mercy.