The phrase "number increases" is correct and usable in written English.
It typically refers to an increase in the quantity of something. For example, "The number of student enrollments increases each year."
The number increases each year.
"As the number increases, the risk increases," he said.
This number increases to 10 officers at music festivals.
This number increases to 80% for churches based in council estates.
If you add families that currently live in inadequate homes, the number increases exponentially.
Between 1995 and 2000 the number increases by 40percentnt.
If Matsuzaka is behind in the count, the number increases to 58percentt.
HEDD has exposed more than 130 examples and this number increases daily.
The number increases daily, but shelter, food and medical support are difficult to come by in the camps.
In the ultrasound scene, the number increases rapidly, a humorous nod to the cost of raising children.
She names them alphabetically, and a good thing too, because keeping order as their number increases is difficult.
