1191018991 has 2 divisors, whose sum is σ = 1191018992. Its totient is φ = 1191018990.

The previous prime is 1191018989. The next prime is 1191019003. The reversal of 1191018991 is 1998101911.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1191018991 - 2¹ = 1191018989 is a prime.

Together with 1191018989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1191018901) 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 as a sum of consecutive naturals, namely, 595509495 + 595509496.

It is an arithmetic number, because the mean of its divisors is an integer number (595509496).

Almost surely, 2^1191018991 is an apocalyptic number.

1191018991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1191018991 is an equidigital number, since it uses as much as digits as its factorization.

1191018991 is an odious number, because the sum of its binary digits is odd.

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

The square root of 1191018991 is about 34511.1429975885. The cubic root of 1191018991 is about 1060.0008873257. Note that the first 3 decimals are identical.

The spelling of 1191018991 in words is "one billion, one hundred ninety-one million, eighteen thousand, nine hundred ninety-one".