Claude Opus 5 aces 20x20-digit multiplication eval, 1200/1200 correct with max reasoning
maksym_andr · x · 2026-09-17
Developer maksymandr ran a minimal eval testing whether frontier LLMs can multiply large numbers without external tools. Claude Opus 5 scored 100% on multiplications up to 20x20 digits (1200/1200 correct), but only at maximum reasoning effort.
The author argues this simple eval is newly relevant for measuring no-CoT capability, especially for recurrent-depth architectures like GPT-6-Astra, which reportedly cannot run without CoT at all.
Related event: Frontier LLMs Nail 20-Digit Multiplication Without Tools(9 posts)→
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