We simply do not know.
We can assume that the twelve were there (the 11 original disciples and Matthias who replaced Judas Iscariot after his suicide), but in addition to these it is most likely that other followers of Jesus were there too. These would have included those who were present at his crucifixion (eg Mary, his mother and Mary Magdalene and Salome, as well as others) and probably other followers such as Cleopas and his friend (thetwo men the resurrected Jesus appeared to on the road to Emmaus), John Mark, Lazarus, Mary and Marha from Bethany, Joseph of Arimathea and possibly Nicodemus too. However as to actual numbers nowhere in scripture does it tell us this - only that 'all' the believers were assembled.
Actually there were just shy of 120.
13And when they were come in, they went up into an upper room, where abode both Peter, and James, and John, and Andrew, Philip, and Thomas, Bartholomew, and Matthew, James the son of Alphaeus, and Simon Zelotes, and Judas the brother of James.
14These all continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brethren.
15And in those days Peter stood up in the midst of the disciples, and said, (the number of names together were about an hundred and twenty.
forty days
49 The seventh Sunday after Easter, commemorating the descent of the Holy Spirit upon the disciples.
Pentecost is celebrated 50 days after Easter.
Only eleven disciples were filled with the holy spirit on Pentecost day. As Judas had committed suicide.
49
At least 12 people.
Ascension is the fortieth day after Easter and Pentecost the fiftieth. In the liturgical year, they are usually celebrated on the following Sunday.
The Pentecost is usually seven weeks after Easter Sunday. The Pentecost usually comes 50 days after Easter. The days counted include Easter Day.
It is 50 days after Easter.50 days
Pentecost was fifty days after passover and Jesus ascended forty days after the resurrection. I believe the answer is pentecost occurred one week after the ascension.
Pentecost Sunday is 49 days after Easter Sunday.
The total number of days spent in the upper room, as described in the New Testament, is traditionally considered to be ten days. This period began after Jesus' ascension and concluded with the Day of Pentecost when the Holy Spirit descended upon the apostles. The apostles, along with other followers, were gathered in the upper room during this time for prayer and preparation.