188991 has 24 divisors (see below), whose sum is σ = 314496. Its totient is φ = 108240.

The previous prime is 188983. The next prime is 188999. The reversal of 188991 is 199881.

It is an interprime number because it is at equal distance from previous prime (188983) and next prime (188999).

It is not a de Polignac number, because 188991 - 2³ = 188983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (188999) 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 23 ways as a sum of consecutive naturals, for example, 2236 + ... + 2318.

It is an arithmetic number, because the mean of its divisors is an integer number (13104).

2¹⁸⁸⁹⁹¹ is an apocalyptic number.

188991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

188991 is a deficient number, since it is larger than the sum of its proper divisors (125505).

188991 is a wasteful number, since it uses less digits than its factorization.

188991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123 (or 120 counting only the distinct ones).

The product of its digits is 5184, while the sum is 36.

The square root of 188991 is about 434.7309512791. The cubic root of 188991 is about 57.3870245491.

It can be divided in two parts, 18 and 8991, that added together give a palindrome (9009).

The spelling of 188991 in words is "one hundred eighty-eight thousand, nine hundred ninety-one".