30 (number)

← 29 30 31 →
← 30 31 32 33 34 35 36 37 38 39 → List of numbers — Integers ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	thirty
Ordinal	30th (thirtieth)
Numeral system	trigesimal
Factorization	2 × 3 × 5
Divisors	1, 2, 3, 5, 6, 10, 15, 30
Roman numeral	XXX
Binary	111102
Ternary	10103
Quaternary	1324
Quinary	1105
Senary	506
Octal	368
Duodecimal	2612
Hexadecimal	1E16
Vigesimal	1A20
Base 36	U36

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.

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