# 30 (number)

30 (thirty) is the natural number following 29 and preceding 31.

 List of numbers — Integers << 30 31 32 33 34 35 36 37 38 39 >>
Cardinalthirty
Ordinalthirtieth
Numeral system
Factorization[itex]2\cdot 3\cdot 5[itex]
Divisors2, 3, 5, 6, 10, 15
Roman numeralXXX
Binary11110
Hebrewל (Lamed)

## In mathematics

It is a primorial as well as the sum of the squares of the integers 1, 2, 3 and 4. It is the first sphenic number and the first Giuga number. It is the sum of the first four squares, which makes it a square pyramidal number.

30 is the largest number such that coprimes smaller than itself are also prime. It is a Harshad number.

The Chinese word numeral for thirty is 三十.

A polygon with thirty sides is called a tricontagon. Both an icosahedron and a dodecahedron have 30 edges.

## In other fields

Thirty is:

• Art and Cultures
• Musical Instruments (http://academickids.com/encyclopedia/index.php/List_of_musical_instruments)
• Countries of the World (http://www.academickids.com/encyclopedia/index.php/Countries)
• Ancient Civilizations (http://www.academickids.com/encyclopedia/index.php/Ancient_Civilizations)
• Industrial Revolution (http://www.academickids.com/encyclopedia/index.php/Industrial_Revolution)
• Middle Ages (http://www.academickids.com/encyclopedia/index.php/Middle_Ages)
• United States (http://www.academickids.com/encyclopedia/index.php/United_States)
• World History (http://www.academickids.com/encyclopedia/index.php/History_of_the_world)
• Human Body (http://www.academickids.com/encyclopedia/index.php/Human_Body)
• Physical Science (http://www.academickids.com/encyclopedia/index.php/Physical_Science)
• Social Studies (http://www.academickids.com/encyclopedia/index.php/Social_Studies)
• Space and Astronomy
• Solar System (http://www.academickids.com/encyclopedia/index.php/Solar_System)