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Sum 25 Divisors

 Published on Monday, 5th October 2026, 06:00 pm and solved by 110

Problem 1013

The number $13521270961$ is the first number that has exactly $25$ divisors and the sum of those divisors is divisible by $25$.

Find the sum of all numbers less than $10^{15}$ that have exactly $25$ divisors and the sum of those divisors is divisible by $25$.



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