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不是网上的内容，是孩子数学书上的，英语不好解释不了，特来求助。 1 First number --One is not a prime number. It's called the "multiplicative identity", because any number multiplied by 1 gives that number as the answer. 2 Even prime number --The number 2 is the only even-numbered prime number - a number that is only divisible by itself and 1。 3 Triangular number --This is smallest triangular number, which is a positive whole number that is the sum of consecutive whole numbers. So, 1+2=3。 4 Composite number --The number 4 is the smallest composite number - a number that is the product of other numbers. The factors of 4 are two 2s. 5 Prime number --This is the only prime number to end with a 5. A 5-sided polygon is the only shape for which the number of sides and diagonals are equal. 6 Perfect number --This is the smallest perfect number, which is a number that is the sum of its positive divisors (except itself). So, 1+2+3=6. 7 Not the sum of squares --The number 7 is the lowest number that cannot be represented as the sum of the squares of three whole numbers (integers). 8 Fibonacci number --The number 8 is a cube number(2^3=8) and it is the only positive Fibonacci number, other than 1, that is a cube. 9 Highest decimal --The number 9 is the highest single-digit whole number and the highest single-digit number in the decimal system. 10 Base number --The Western number system is based on the number 10. It is speculated that this is because humans used their fingers and toes for counting. |
