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Problem 926


Problem 926


Total Roundness

A round number is a number that ends with one or more zeros in a given base.

Let us define the roundness of a number n in base b as the number of zeros at the end of the base b representation of n.

For example, 20 has roundness 2 in base 2, because the base 2 representation of 20 is 10100, which ends with 2 zeros.

Also define R(n), the total roundness of a number n, as the sum of the roundness of n in base b for all b>1.

For example, 20 has roundness 2 in base 2 and roundness 1 in base 4, 5, 10, 20, hence we get R(20)=6.

You are also given R(10!)=312.

Find R(10 000 000!). Give your answer modulo 109+7.


总取整度

取整数是指在给定进制下以一个或多个零结尾的数。

定义数n在进制b下的取整度nb进制表示下末尾零的个数。

例如,202进制下的取整度为2,因为202进制表示是10100,末尾有2个零。

再定义R(n)为数n总取整度,即n在所有b>1的进制b下的取整度之和。

例如,202进制下的取整度为2,在451020进制下的取整度为1,因此R(20)=6

已知R(10!)=312

R(10 000 000!),并对109+7取余作为你的答案。


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