1159991 has 4 divisors (see below), whose sum is σ = 1325712. Its totient is φ = 994272.

The previous prime is 1159981. The next prime is 1159993. The reversal of 1159991 is 1999511.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1159991 - 2¹⁸ = 897847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1159993) 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, 82850 + ... + 82863.

It is an arithmetic number, because the mean of its divisors is an integer number (331428).

2^1159991 is an apocalyptic number.

1159991 is a deficient number, since it is larger than the sum of its proper divisors (165721).

1159991 is an equidigital number, since it uses as much as digits as its factorization.

1159991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165720.

The product of its digits is 3645, while the sum is 35.

The square root of 1159991 is about 1077.0287832737. The cubic root of 1159991 is about 105.0714857119.

The spelling of 1159991 in words is "one million, one hundred fifty-nine thousand, nine hundred ninety-one".