1165991 has 2 divisors, whose sum is σ = 1165992. Its totient is φ = 1165990.

The previous prime is 1165951. The next prime is 1165993. The reversal of 1165991 is 1995611.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (1995611) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1165991 - 2¹⁰ = 1164967 is a prime.

Together with 1165993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1165993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 582995 + 582996.

It is an arithmetic number, because the mean of its divisors is an integer number (582996).

2^1165991 is an apocalyptic number.

1165991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1165991 is an equidigital number, since it uses as much as digits as its factorization.

1165991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2430, while the sum is 32.

The square root of 1165991 is about 1079.8106315461. The cubic root of 1165991 is about 105.2523334001.

The spelling of 1165991 in words is "one million, one hundred sixty-five thousand, nine hundred ninety-one".