139 (number)
From Halbeeg, the open encyclopedia · Af-Soomaali
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139 is a natural number that comes after 138 and before 140. It is a three-digit number written in decimal notation. Like other numbers, it has two basic uses: cardinal ("one hundred thirty-nine") and ordinal ("the 139th").
The most significant property mathematically is that 139 is a prime number, meaning it is divisible only by 1 and itself. Its divisors are therefore 1 and 139, and their sum is 140.
Mathematical properties
139 is the 34th prime number, starting from 2. It forms a pair of twin primes with 137, since the difference between them is two. It can also be expressed as the sum of five consecutive primes: 19 + 23 + 29 + 31 + 37 = 139.
When 139 is divided by 4, the remainder is 3. This property means 139 cannot be written as the sum of two squares, in accordance with Fermat's theorem on primes. When the digits are processed sequentially, 139 also belongs to the class known as "happy numbers", since repeated summing of the squares of its digits eventually reaches 1.
Notation and other systems
In Roman numerals, 139 is written CXXXIX. In binary it is 10001011, while in hexadecimal it is 8B. In Arabic-Hindu numerals, which Somali commonly uses, it consists of three digits: 1, 3, and 9.
Common usage
Numbers like 139 appear in various numbering systems: article numbers in constitutions and laws, road numbers, numbers assigned to countries in international organization lists, and technological rankings. The meaning of the number depends on the system in which it is used, not on the number itself.