- published: 30 Jun 2016
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30 (thirty) is the natural number following 29 and preceding 31.
30 is the sum of the first four squares, which makes it a square pyramidal number.
It is a primorial and is the smallest Giuga number.
30 is the smallest sphenic number, and the smallest of the form 2 × 3 × r, where r is a prime greater than 3. 30 has an aliquot sum of 42; the second sphenic number and all sphenic numbers of this form have an aliquot sum 12 greater than themselves. The aliquot sequence of 30 is 16 members long, it comprises (30,42,54,66,78,90,144,259,45,33,15,9,4,3,1,0)
Thirty has but one number for which it is the aliquot sum: the square number 841.
Adding up some subsets of its divisors (e.g., 5, 10 and 15) gives 30, hence 30 is a semiperfect number.
30 is the largest number such that all coprimes smaller than itself, except for 1, are prime.
A polygon with thirty sides is called a triacontagon.
The icosahedron and the dodecahedron are Platonic solids with 30 edges. The icosidodecahedron is an Archimedean solid with 30 vertices, and the Tutte–Coxeter graph is a symmetric graph with 30 vertices.
Knowing
Is what people tell you
That you're thinking wrong
Embrace you,
But they really mean 'So long'
You talk to them
They laugh aloud
Yet they run to you
In any crowd
Please talk to me again
I need you
We're dancing
We will come and dance near you
We want to learn
Let us come and sitar with you
Distort my ears when
The music's loud
Yet you raise your hatchet
In the yellow crowd
Please talk to me again
I need you
Knowing
Is what people tell you
That you're thinking wrong
Embrace you,
But they really mean 'So long'
You talk to them
They laugh aloud
Yet they run to you
In any crowd
Please talk to me again
I need you