139

139 is a prime number.

137 and 139 form a twin prime pair.

139 is a divisor of 42³ - 1.

139 is the smallest prime that retains the end (unit) digit of its successor (149). 139 and 149 are the first consecutive primes differing by 10.

139 is the smallest prime with one prime digit, one composite digit, and one digit that is neither prime nor composite.

139 divides the sum of the first 139 composite numbers.

139 is the smallest prime number whose product of digits is a prime cube: 1 x 3 x 9 = 27 = 3³.

139 Juewa is a large, dark, main-belt asteroid discovered in 1874.

Source: Number Gossip