11111991 has 8 divisors (see below), whose sum is σ = 16162944. Its totient is φ = 6734520.

The previous prime is 11111983. The next prime is 11111993. The reversal of 11111991 is 19911111.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 11111991 - 2³ = 11111983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11111993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 168331 + ... + 168396.

It is an arithmetic number, because the mean of its divisors is an integer number (2020368).

Almost surely, 2^11111991 is an apocalyptic number.

11111991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

11111991 is a deficient number, since it is larger than the sum of its proper divisors (5050953).

11111991 is a wasteful number, since it uses less digits than its factorization.

11111991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 336741.

The product of its digits is 81, while the sum is 24.

The square root of 11111991 is about 3333.4653140538. The cubic root of 11111991 is about 223.1502068047.

The spelling of 11111991 in words is "eleven million, one hundred eleven thousand, nine hundred ninety-one".