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Smallest number one short of a multiple of 2 to 10

Question

What is the least positive integer NN such that, for each k=2,3,…,10k=2,3,\dots,10, dividing NN by kk leaves remainder k−1k-1?

Short answer

25192519. The condition says N+1N+1 is divisible by every kk from 22 to 1010, so N+1N+1 is a multiple of lcm⁡(2,…,10)=2520\operatorname{lcm}(2,\dots,10)=2520. The smallest choice is N=2519N=2519.

Adapted from Crack, Heard on the Street, Q1.27, p.14; question and answer rewritten by SelfMadeQuant.com.

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