O b v i o u s Obvious is a D a n g e r o u s Dangerous w o r d word in Mathematics

Let N N denote the two-digit number whose cube root is the square root of the sum of its digits. How many positive divisors does N N have?

2 3 4 5 6 8

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4 solutions

Vaibhav Prasad
Feb 23, 2015

First of all, the number should be a cube .

Secondly, it should be a two digit number.

We get : 27 27 and 64 64

27 27 satisfies the conditions.

And 27 27 has 1 , 3 , 9 , 27 1,3,9,27 as factors .

hahhahahah, nice :D

Paul Ryan Longhas - 6 years, 3 months ago
Noel Lo
May 21, 2015

The number is 27!!!

David Holcer
Apr 18, 2015
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from math import *
def factors(n):    
    return set(reduce(list.__add__, 
                ([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0)))
def sum(n):
    summ=0
    for i in str(n):
        summ+=int(i)
    return summ
for i in range(10,100):
    if i**(1/float(3))==float(sqrt(sum(i))):
        print len(factors(i))

I used same approach, but checked it with code :)

Paul Ryan Longhas
Feb 23, 2015

There are only two two-digit cubes and this are 27 27 and 64 64 .

OBVIOUS that only 27 27 satisfies the condition.

Since 27 27 has 4 4 divisors = > 4 => 4 is answer

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