118191991 has 4 divisors (see below), whose sum is σ = 118531000. Its totient is φ = 117852984.

The previous prime is 118191977. The next prime is 118192001. The reversal of 118191991 is 199191811.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-118191991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (118191901) 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, 168981 + ... + 169678.

It is an arithmetic number, because the mean of its divisors is an integer number (29632750).

Almost surely, 2^118191991 is an apocalyptic number.

118191991 is a deficient number, since it is larger than the sum of its proper divisors (339009).

118191991 is an equidigital number, since it uses as much as digits as its factorization.

118191991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 339008.

The product of its digits is 5832, while the sum is 40.

The square root of 118191991 is about 10871.6140016099. The cubic root of 118191991 is about 490.7526832866.

The spelling of 118191991 in words is "one hundred eighteen million, one hundred ninety-one thousand, nine hundred ninety-one".