geometric number
nounUK /ˌdʒiːəˈmetrɪk ˈnʌmbə/
US /ˌdʒiəˈmɛtrɪk ˈnʌmbər/
A geometric number is a number you can make into a neat shape with dots, like a triangle or a square.
Ten is a geometric number because you can arrange ten dots into a triangle.
OTHER MEANINGS
2. A number that counts the dots in a regular geometric arrangement.
The fourth triangular geometric number is ten.
3. A number belonging to a sequence built from growing shapes.
Square geometric numbers go 1, 4, 9, 16, and so on.
4. A number that can be shown as a polygon of evenly spaced points.
Fifteen is a geometric number that forms a pentagon of dots.