Owlet puzzle #72
Released Tuesday, September 15, 2026 UTC
127
the answer for puzzle #72
The five clues
- A three-digit number ending in seven, under 150.
- A prime one less than a power of two.
- A Mersenne prime: 2^n − 1 for some prime n.
- It equals 2⁷ − 1.
- Its digits sum to 10 and it is a double Mersenne — 2^(2⁷−1)−1 is also famously worked on in the search for larger primes.
Backstory
127 = 2⁷ − 1 is the fourth Mersenne prime, and one of the four Mersenne primes known to Pietro Cataldi by 1588 (with 3, 7, and 31). It's also the 31st prime overall (with exponent 7 in the Mersenne form), and appears in the ASCII table as DEL — the highest 7-bit code.
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