- 2 - Wikipedia
2 (two) is a number, numeral and digit It is the natural number following 1 and preceding 3 It is the smallest and the only even prime number Because it forms the basis of a duality, it has religious and spiritual significance in many cultures The number 2 is the second natural number, after 1
- 2（自然数之一）_百度百科
2：是一个自然数，同时也是1和3之间的正整数，也是偶数。 如果一个数能被2整除，就是偶数，反之则是奇数。 2是最小的质数（也叫素数），也是唯一的偶质数，只有1、2两个因数，是一个有理数。 2也是黑格纳数。
- 2 (number) - New World Encyclopedia
The glyph currently used in the Western world to represent the number 2 traces its roots back to the Brahmin Indians, who wrote 2 as two horizontal lines (It is still written that way in modern Chinese and Japanese )
- 2 - Wiktionary, the free dictionary
A West Arabic numeral, ultimately from Indic numerals (compare Devanagari २ (2)), from a cursive form of two lines to represent the number two See 2 § Evolution for more
- 2的次方表（1~64次方）-CSDN博客
1 2 的 次方：从 1次方 到 1 0 次方 依次是 2, 4, 8, 1 6, 3 2, 64, 12 8, 2 56, 5 12, 1 0 2 4。 这个序列反映了 2 的指数增长，每增加一次幂，结果翻倍。 2 3的 次方：从 1次方 到 1 0 次方 是3, 9, 2 7, 8 1, 2 43, 7 2 9, 21 87, 656 1, 1 9683, 文章浏览阅读10w+次，点赞173次，收藏384次。
- 2 -- from Wolfram MathWorld
The number two (2) is the second positive integer and the first prime number It is even, and is the only even prime (the primes other than 2 are called the odd primes) The number 2 is also equal to its factorial since 2!=2 A quantity taken to the power 2 is said to be squared
- Number 2 - Facts about the integer - Numbermatics
Cardinal: 2 can be written as Two 2 is a deficient number, because the sum of its proper divisors (1) is less than itself Its deficiency is 1 How big is 2? A cube with a volume of 2 cubic inches would be around 0 1 feet tall 2 is the same when its digits are reversed! That makes it a palindromic prime number 2 is a Harshad number
- 2 - 维基百科，自由的百科全书
对于用偶数进制书写的整数，例如 十進制 和 十六進制，要判断它是否为偶数，只需判断最后一位是否为偶数，而2進位則只需判断最后一位是否为0。
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