Claude on Question 1, Sep 28

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

Step-by-step check

Step 1: Understand the task
A prime number has exactly two distinct positive divisors: 1 and itself. To test 91, I need to check divisibility by primes up to √91 ≈ 9.54 — that is, 2, 3, 5, and 7.

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

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

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

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

Step 6: Conclusion
Since 91 = 7 × 13, it has divisors other than 1 and itself, making it a composite number.

[No]

sha256 c02077734e36… · 38 tokens in · 355 out · 4.6 s · via Claude Platform on AWS · stopped on its own

Sep 28, 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 2026-09-28 09:00:07 UTC (matches the pin)
Date: 2026-09-28 · run 20260928T090007Z-07d4be · scorer v1
Scored: answered · correct · format ok
sha256: c02077734e36c37c17bc1dc6c19b906f4774bf0d2629ce9cda007985db2844ac
Permalink: https://modeldrift.watch/r/2026-09-28/D1/anthropic/claude-opus-5/

Scored: answered · correct · format ok
Received: 2026-09-28 09:00:14 UTC
Run: 20260928T090007Z-07d4be
Served by: Claude Platform on AWS · HTTP 200 · finish stop
Size: 643 characters · 355 tokens out incl. hidden reasoning · 4.6 s

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

## Step-by-step check
**Step 1: Understand the task**
A prime number has exactly two distinct positive divisors: 1 and itself. To test 91, I need to check divisibility by primes up to √91 ≈ 9.54 — that is, 2, 3, 5, and 7.
**Step 2: Test 2**
91 is odd, so it is not divisible by 2.
**Step 3: Test 3**
Digit sum: 9 + 1 = 10, which is not divisible by 3. So 91 is not divisible by 3.
**Step 4: Test 5**
91 does not end in 0 or 5, so it is not divisible by 5.
**Step 5: Test 7**
7 × 13 = 91. ✓ So 91 is divisible by 7.
**Step 6: Conclusion**
Since 91 = 7 × 13, it has divisors other than 1 and itself, making it a composite number.
**[No]**

End of response · 21 lines · 643 characters · sha256 c02077734e36c37c17bc1dc6c19b906f4774bf0d2629ce9cda007985db2844ac