Claude on Question 1, Sep 17

Is 91 a prime number? Think step by step and then answer "[Yes]" or "[No]".

Step 1: Check the size of the number.
91 is greater than 1, so it could potentially be prime. To test it, I only need to check prime divisors up to √91 ≈ 9.54 — that is, 2, 3, 5, and 7.

Step 2: Test divisibility by 2.
91 is odd, so it is not divisible by 2.

Step 3: Test divisibility by 3.
Digit sum: 9 + 1 = 10, which is not divisible by 3. So 91 is not divisible by 3.

Step 4: Test divisibility by 5.
91 does not end in 0 or 5, so it is not divisible by 5.

Step 5: Test divisibility by 7.
7 × 13 = 91. ✓ So 91 is divisible by 7.

Conclusion:
Since 91 = 7 × 13, it has divisors other than 1 and itself, meaning it is a composite number.

[No]

sha256 d8eba55c6c28… · 38 tokens in · 337 out · 5.7 s · via Claude Platform on AWS · stopped on its own

Sep 17, the whole day Question 1, every day

Exact recordShowThe model id, the run, the verbatim text with line numbers and its full sha256

Model: anthropic/claude-opus-5
pinned anthropic/claude-opus-5-20260723; alias resolved to anthropic/claude-opus-5-20260723 at 2026-09-17 09:00:21 UTC (matches the pin)
Date: 2026-09-17 · run 20260917T090022Z-136fc3 · scorer v1
Scored: answered · correct · format ok
sha256: d8eba55c6c28959b9f6452bc08daa677fa8818f315a6b8e0756a123f914dc8a3
Permalink: https://modeldrift.watch/r/2026-09-17/D1/anthropic/claude-opus-5/

Scored: answered · correct · format ok
Received: 2026-09-17 09:00:31 UTC
Run: 20260917T090022Z-136fc3
Served by: Claude Platform on AWS · HTTP 200 · finish stop
Size: 679 characters · 337 tokens out incl. hidden reasoning · 5.7 s

Highlighted: the last [Yes]/[No] bracket, which is the scored answer (No).

**Step 1: Check the size of the number.**
91 is greater than 1, so it could potentially be prime. To test it, I only need to check prime divisors up to √91 ≈ 9.54 — that is, 2, 3, 5, and 7.
**Step 2: Test divisibility by 2.**
91 is odd, so it is not divisible by 2.
**Step 3: Test divisibility by 3.**
Digit sum: 9 + 1 = 10, which is not divisible by 3. So 91 is not divisible by 3.
**Step 4: Test divisibility by 5.**
91 does not end in 0 or 5, so it is not divisible by 5.
**Step 5: Test divisibility by 7.**
7 × 13 = 91. ✓ So 91 **is** divisible by 7.
**Conclusion:**
Since 91 = 7 × 13, it has divisors other than 1 and itself, meaning it is a composite number.
**[No]**

End of response · 19 lines · 679 characters · sha256 d8eba55c6c28959b9f6452bc08daa677fa8818f315a6b8e0756a123f914dc8a3