1191909091 has 4 divisors (see below), whose sum is σ = 1212111000. Its totient is φ = 1171707184.

The previous prime is 1191909071. The next prime is 1191909101. The reversal of 1191909091 is 1909091911.

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-1191909091 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1191909011) 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, 10100866 + ... + 10100983.

It is an arithmetic number, because the mean of its divisors is an integer number (303027750).

Almost surely, 2^1191909091 is an apocalyptic number.

1191909091 is a deficient number, since it is larger than the sum of its proper divisors (20201909).

1191909091 is an equidigital number, since it uses as much as digits as its factorization.

1191909091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20201908.

The product of its (nonzero) digits is 6561, while the sum is 40.

The square root of 1191909091 is about 34524.0364239178. The cubic root of 1191909091 is about 1060.2648830731.

The spelling of 1191909091 in words is "one billion, one hundred ninety-one million, nine hundred nine thousand, ninety-one".