1091999 has 4 divisors (see below), whose sum is σ = 1095864. Its totient is φ = 1088136.

The previous prime is 1091983. The next prime is 1092019. The reversal of 1091999 is 9991901.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9991901 = 71 ⋅140731.

It is a cyclic number.

It is not a de Polignac number, because 1091999 - 2⁴ = 1091983 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 (1091939) 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 in 3 ways as a sum of consecutive naturals, for example, 1472 + ... + 2085.

It is an arithmetic number, because the mean of its divisors is an integer number (273966).

2^1091999 is an apocalyptic number.

1091999 is a deficient number, since it is larger than the sum of its proper divisors (3865).

1091999 is an equidigital number, since it uses as much as digits as its factorization.

1091999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3864.

The product of its (nonzero) digits is 6561, while the sum is 38.

The square root of 1091999 is about 1044.9875597346. The cubic root of 1091999 is about 102.9771212577.

The spelling of 1091999 in words is "one million, ninety-one thousand, nine hundred ninety-nine".