191691 has 18 divisors (see below), whose sum is σ = 297180. Its totient is φ = 119016.

The previous prime is 191689. The next prime is 191693. The reversal of 191691 is 196191.

191691 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (191689) and next prime (191693).

It is not a de Polignac number, because 191691 - 2¹ = 191689 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

Its product of digits (486) is a multiple of the sum of its prime divisors (81).

191691 is strictly pandigital in base 7.

It is not an unprimeable number, because it can be changed into a prime (191693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 3220 + ... + 3278.

It is an arithmetic number, because the mean of its divisors is an integer number (16510).

2¹⁹¹⁶⁹¹ is an apocalyptic number.

191691 is a deficient number, since it is larger than the sum of its proper divisors (105489).

191691 is a wasteful number, since it uses less digits than its factorization.

191691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103 (or 81 counting only the distinct ones).

The product of its digits is 486, while the sum is 27.

The square root of 191691 is about 437.8253076285. The cubic root of 191691 is about 57.6590179229.

The spelling of 191691 in words is "one hundred ninety-one thousand, six hundred ninety-one".