127

127 is a prime number.

127 is a Mersenne number: 2⁷ – 1 = 127. It is the largest Mersenne prime with all different digits.

127 = 2⁰ + 2¹ + 2² + 2³ + 2⁴ + 2⁵ + 2⁶.

127 can be expressed as the sum of factorials of the first three odd numbers: 1! + 3! + 5! = 127.


127 is the number of prime days in a leap year.

Source: Prime Curios!