66606...66601 (65-digits)

This number is a prime.

     66606 6606660666 0666066606 6606660666 0666066606 6606660666 0666066601

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The largest prime p less than a googol formed from n strings of “6660”, followed by 1, (n=16). Note that p ends with the smallest non-palindromic beastly prime (66601). Also, p is expressible as the sum of two squares: (241095534445013465071393494681275^2 + 92084764954578303280732847232324^2). [Bajpai]