30 mph speed limit sign

30

= 2 × 3 × 5

= 2 × 15
= 3 × 10
= 5 × 6

= 2 + 4 + 6 + 8 + 10
= 4 + 5 + 6 + 7 + 8

= 1 + 4 + 9 + 16
A pyramidal number - the sum of the first four square numbers.

There are 30 days in April, June, September and November.

Dodecahedrons and icosahedrons both have 30 edges.

30 mph is the UK speed limit for vehicles driving in a built up area.

'Score below 30 to win' sign at fairground stall.

The base of this pyramid is a 4 × 4 square with smaller squares resting on it.
30 is a pyramidal number. The base of this pyramid is a 4 × 4 square with smaller squares resting on it.

Thirty something was a television drama series about American yuppies in their thirties.

The Thirty Years' War was a European war from 1618 to 1648.

In old British money half-a-crown (or half-a-dollar) was a coin worth 30 old pence.

A pearl anniversary celebrates 30 years.

The best known feature of Stonehenge is the Sarsen Circle which was built as 30 upright stones with 30 lintel stones on top of them. Only 16 remain standing today.

Number 30