1128991 has 4 divisors (see below), whose sum is σ = 1132912. Its totient is φ = 1125072.

The previous prime is 1128979. The next prime is 1128997. The reversal of 1128991 is 1998211.

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 1128991 - 2¹³ = 1120799 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 (1128997) 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, 1491 + ... + 2116.

It is an arithmetic number, because the mean of its divisors is an integer number (283228).

2^1128991 is an apocalyptic number.

1128991 is a deficient number, since it is larger than the sum of its proper divisors (3921).

1128991 is an equidigital number, since it uses as much as digits as its factorization.

1128991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3920.

The product of its digits is 1296, while the sum is 31.

The square root of 1128991 is about 1062.5398816045. The cubic root of 1128991 is about 104.1270328863.

The spelling of 1128991 in words is "one million, one hundred twenty-eight thousand, nine hundred ninety-one".