Problems

1 – 12 of 12

Problem Title Likes Solvers Difficulty

Problem 44862. Ratio between sum of primes and sum of factors

Created by: Jesús Zambrano

Tags primes, factors, ratio

Problem 44229. How brilliant are you?

Created by: James

Tags factors, number theory, brilliant

Problem 1804. Fangs of a vampire number

Created by: Andrew Newell

Tags factors, number theory

Problem 54144. Factor Digits

Created by: Dyuman Joshi

Tags factors, prime factors

Problem 656. Calculate Euler's phi function

Created by: Freddy

Tags math, basic matlab, factors

Problem 365. Numbers with prime factors 2, 3 and 5.

Created by: elias GR

Tags primes, factors

408

Problem 54680. Determine whether a number is practical

Created by: ChrisR

Tags factors, number theory, sequence

Problem 1925. Smith numbers

Created by: Sky Sartorius

Tags sum, factors

484

Problem 1825. Find all vampire fangs

Created by: Andrew Newell

Tags factors, number theory

Problem 3075. Matrix of Multiplication Facts

Created by: James

Tags matrix, factors, elementary_school_math

Problem 577. Repopulate the City

Created by: Ned Gulley

Tags factors

Problem 1826. Find vampire numbers

Created by: Andrew Newell

Tags factors, number theory

279

1 – 12 of 12

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Problem Groups

Difficulty Rating

Problem Groups

Problems

Problem 44862. Ratio between sum of primes and sum of factors

Problem 44229. How brilliant are you?

Problem 1804. Fangs of a vampire number

Problem 54144. Factor Digits

Problem 656. Calculate Euler's phi function

Problem 365. Numbers with prime factors 2, 3 and 5.

Problem 54680. Determine whether a number is practical

Problem 1925. Smith numbers

Problem 1825. Find all vampire fangs

Problem 3075. Matrix of Multiplication Facts

Problem 577. Repopulate the City

Problem 1826. Find vampire numbers