The phrase "a number of active" is correct and usable in written English.
It can be used when referring to several individuals or entities that are currently engaged in a particular activity or state.
Example: "A number of active participants joined the discussion to share their insights."
Alternatives: "several active" or "many active".
The source of this pharmacological activity is a number of active components of which glycyrrhizic acid (GA) is considered the most important.
Indeed, the Europeans have successfully uncovered and dismantled a number of active cells in their countries.
On the contrary, he expects a number of active players to be on hand Thursday for the news conference.
Dominica has a number of active volcanoes, although eruptions are rare.
Poneman said there are a number of active deals under development, and strong public support for nuclear power, but that capital costs continue to be a challenge.
The Sons of Norway, a Norwegian American cultural and educational organization, has a number of active chapters in the state.
In early 1971, a major development occurred with the introduction of current, computerized quotations on a number of active stocks.
At any moment a large cloud may contain a number of active thermals and the residues of earlier ones.
A number of active duty and retired senior officers say there is concern that the president is moving too slowly, is revisiting a war strategy he announced in March and is unduly influenced by political advisers in the Situation Room.
He had became involved in an ugly, two-year dispute with retired players while a number of active players had begun to complain of a disconnect with the union.
Ecuador, which sits on the seismically volatile part of the the Pacific basin called the Ring of Fire, has a number of active volcanoes and regular small earthquakes, so, although the reverberations were worrisome, they were also familiar to Orellana.
