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Largest integer divisible by two primes

Problem 347

Published on Saturday, 3rd September 2011, 04:00 pm; Solved by 1424

The largest integer ≤ 100 that is only divisible by both the primes 2 and 3 is 96, as 96=32*3=25*3. For two distinct primes p and q let M(p,q,N) be the largest positive integer ≤N only divisible by both p and q and M(p,q,N)=0 if such a positive integer does not exist.

E.g. M(2,3,100)=96.
M(3,5,100)=75 and not 90 because 90 is divisible by 2 ,3 and 5.
Also M(2,73,100)=0 because there does not exist a positive integer ≤ 100 that is divisible by both 2 and 73.

Let S(N) be the sum of all distinct M(p,q,N). S(100)=2262.

Find S(10 000 000).