918999991 has 32 divisors (see below), whose sum is σ = 1236307968. Its totient is φ = 662238720.

The previous prime is 918999979. The next prime is 919000001. The reversal of 918999991 is 199999819.

It is not a de Polignac number, because 918999991 - 2⁷ = 918999863 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (918999901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 38376 + ... + 57538.

It is an arithmetic number, because the mean of its divisors is an integer number (38634624).

Almost surely, 2^918999991 is an apocalyptic number.

918999991 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

918999991 is a deficient number, since it is larger than the sum of its proper divisors (317307977).

918999991 is a wasteful number, since it uses less digits than its factorization.

918999991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19231.

The product of its digits is 4251528, while the sum is 64.

The square root of 918999991 is about 30315.0126340069. The cubic root of 918999991 is about 972.2363080355.

The spelling of 918999991 in words is "nine hundred eighteen million, nine hundred ninety-nine thousand, nine hundred ninety-one".