Strong's #4004: pentekonta (pronounced pen-tay'-kon-tah)
 multiplicative of 4002; fifty:--fifty.
Thayer's Greek Lexicon:
 ́ 
 
  pentēkonta 
 
 1) fifty
 
  Part of Speech: adjective
Relation: multiplicative of G4002
 
Usage:
This word is used 7 times:
Mark 6:40: "in ranks, by hundreds, and  by fifties."
Luke 7:41: "and the other  fifty."
Luke 9:14: "Make them sit down by  fifties in a company."
Luke 16:6: "sit down quickly, and write  fifty."
John 8:57: "him, Thou art not yet  fifty years old, and hast thou seen Abraham?"
John 21:11: "full of great fishes,  a hundred and fifty and three: and for all there were"
Acts 13:20: "about the space of four hundred and  fifty years, until Samuel the"