191 is nontrivially palindromic in base 6, base 9 and base 10.
191 is an esthetic number in base 9 and base 15, because in such bases its adjacent digits differ by 1.
It is a strong prime.
It is a palprime.
It is a cyclic number.
It is a Sophie Germain prime.
It is a Chen prime.
191 is an undulating number in base 6, base 9 and base 10.
It is a plaindrome in base 4, base 8, base 12, base 13 and base 16.
It is a nialpdrome in base 14 and base 15.
It is a congruent number.
Being equal to 3×43-1, it is a generalized Woodall number.
It is a good prime.
191 is an equidigital number, since it uses as much as digits as its factorization.
It is an anagram of its base 13 representation: 191 = (119)13.
191 is an odious number, because the sum of its binary digits is odd.
The square root of 191 is about 13.8202749611. The cubic root of 191 is about 5.7589652205.
Adding to 191 its sum of digits (11), we get a palindrome (202).
The spelling of 191 in words is "one hundred ninety-one", and thus it is an aban number.