70 (number)
From Halbeeg, the open encyclopedia · Af-Soomaali
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70 is a natural number that lies between 69 and 71. It is a two-digit number in decimal notation, composed of 7 and 0. It is also an even number, divisible by 2.
In mathematics, 70 has several divisors compared to related numbers: 1, 2, 5, 7, 10, 14, 35, and 70. It is a composite number, with prime factorization 2 × 5 × 7. Because it consists of three distinct prime factors each appearing once, it is known as a sphenic number.
Mathematical properties
The sum of the proper divisors of 70 (1+2+5+7+10+14+35) is 74, which exceeds 70. Therefore 70 is an abundant number. It is also called a weird number because although the sum of its proper divisors exceeds the number itself, no subset of those divisors sums exactly to 70. It is the smallest number with this property.
In combinatorics, 70 arises from the central binomial coefficient: C(8,4) = 70. It also relates to sums of squares—though the connection requires verification through mathematical references.
Notation and other systems
In Roman numerals, 70 is written LXX. This notation is also used in the name of the Septuagint, an ancient Greek translation of the Hebrew scriptures (LXX). In binary notation, 70 is 1000110. In hexadecimal, it is 46.
Common usage
70 is commonly used as a conventional measure, such as in counting years of life or group sizes. In Somali, the word is 'todobaatan', derived from 'todoba' (seven) with an affix indicating tens. In measurement systems, 70 appears in common contexts such as 70 percent or 70 degrees.