## Project Euler – Problem 7

From the Project Euler

Problem 7:
By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.
What is the 10001st prime number?

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used the code for problem 3. ## Project Euler – Problem 6

From the Project Euler

Problem 6:
The sum of the squares of the first ten natural numbers is,
1^2 + 2^2 + … + 10^2 = 385
The square of the sum of the first ten natural numbers is,
(1 + 2 + … + 10)^2 = 55^2 = 3025
Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 – 385 = 2640.
Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.

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very easy. ## Project Euler – Problem 5

From the Project Euler

Problem 5:
2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.
What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?

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It ‘s the least common multiple of the numbers between 2 and 20. ## Project Euler – Problem 4

From the Project Euler

Problem 4:
A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 * 99.
Find the largest palindrome made from the product of two 3-digit numbers

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## Project Euler – Problem 3

From the Project Euler

Problem 3:
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?

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I used the Sieve of Eratosthenes and an idea to know if a prime factor was the greatest without checking all the numbers until 600851475143. ## Project Euler 