SIG (Susquehanna)–styleSoftware EngineerSoftware DeveloperQuestion #5
Is 1599 a prime number?
Free worked solution · Quant Blueprint
No. 1599 = 3 × 13 × 41.
- The digit sum is 1 + 5 + 9 + 9 = 24. Because 24 is divisible by three, so is 1599.
- Divide by three to get 533. Finding the factor three already proves that 1599 is composite.
- For a complete prime factorization, 533 = 13 × 41. Both factors are prime, so the factorization is 3 × 13 × 41.
Common mistake
You do not need to test every prime below the square root once you have found one nontrivial divisor.
Follow-up
A general trial-division primality test only needs candidate factors up to √n: if both factors exceeded √n, their product would exceed n.
Original educational explanation for this practice question. Reviewed . Firm-style practice; the label describes the collection’s preparation context.
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