1191091091 has 4 divisors (see below), whose sum is σ = 1191435000. Its totient is φ = 1190747184.

The previous prime is 1191091067. The next prime is 1191091117. The reversal of 1191091091 is 1901901911.

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-1191091091 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1191091051) 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 3 ways as a sum of consecutive naturals, for example, 166706 + ... + 173703.

It is an arithmetic number, because the mean of its divisors is an integer number (297858750).

Almost surely, 2^1191091091 is an apocalyptic number.

1191091091 is a deficient number, since it is larger than the sum of its proper divisors (343909).

1191091091 is an equidigital number, since it uses as much as digits as its factorization.

1191091091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 343908.

The product of its (nonzero) digits is 729, while the sum is 32.

The square root of 1191091091 is about 34512.1875719288. The cubic root of 1191091091 is about 1060.0222764394.

It can be divided in two parts, 11 and 91091091, that multiplied together give a palindrome (1002002001).

The spelling of 1191091091 in words is "one billion, one hundred ninety-one million, ninety-one thousand, ninety-one".