105 (number)

← 104 105 106 →
← 100 101 102 103 104 105 106 107 108 109 → List of numbers — Integers ← 0 100 200 300 400 500 600 700 800 900 →
Cardinal	one hundred five
Ordinal	105th (one hundred fifth)
Factorization	3 × 5 × 7
Divisors	1, 3, 5, 7, 15, 21, 35, 105
Roman numeral	CV
Binary	11010012
Ternary	102203
Quaternary	12214
Quinary	4105
Senary	2536
Octal	1518
Duodecimal	8912
Hexadecimal	6916
Vigesimal	5520
Base 36	2X36

105 (one hundred [and] five) is the natural number following 104 and preceding 106.

105 is a triangular number, a dodecagonal number and the first Zeisel number. It is a sphenic number, and is the product of three consecutive prime numbers. 105 is the double factorial of 7. It is also the sum of the first five square pyramidal numbers.

105 comes in the middle of the prime quadruplet (101, 103, 107, 109). The only other such odd numbers less than a thousand are 9, 15, 195 and 825. 105 is also a pseudoprime to the prime bases 13, 29, 41, 43, 71, 83 and 97. The distinct prime factors of 105 add up to 15, and so do those of 104, hence the two numbers form a Ruth-Aaron pair under the first definition.

105 is also a number n for which ${\displaystyle n-2^{k}}$ is prime, for ${\displaystyle 0<k<log_{2}(n)}$. (This even works up to ${\displaystyle k=8}$, ignoring the negative sign.)

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