188116991 has 4 divisors (see below), whose sum is σ = 193201272. Its totient is φ = 183032712.

The previous prime is 188116987. The next prime is 188117009. The reversal of 188116991 is 199611881.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199611881 = 7 ⋅28515983.

It is a cyclic number.

It is not a de Polignac number, because 188116991 - 2² = 188116987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (188116921) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2542085 + ... + 2542158.

It is an arithmetic number, because the mean of its divisors is an integer number (48300318).

Almost surely, 2^188116991 is an apocalyptic number.

188116991 is a deficient number, since it is larger than the sum of its proper divisors (5084281).

188116991 is an equidigital number, since it uses as much as digits as its factorization.

188116991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5084280.

The product of its digits is 31104, while the sum is 44.

The square root of 188116991 is about 13715.5747601039. The cubic root of 188116991 is about 572.9842369218.

The spelling of 188116991 in words is "one hundred eighty-eight million, one hundred sixteen thousand, nine hundred ninety-one".