1128081991 has 4 divisors (see below), whose sum is σ = 1166981400. Its totient is φ = 1089182584.

The previous prime is 1128081973. The next prime is 1128082013. The reversal of 1128081991 is 1991808211.

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 1128081991 - 2⁵ = 1128081959 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 (1128081901) 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, 19449661 + ... + 19449718.

It is an arithmetic number, because the mean of its divisors is an integer number (291745350).

Almost surely, 2^1128081991 is an apocalyptic number.

1128081991 is a deficient number, since it is larger than the sum of its proper divisors (38899409).

1128081991 is an equidigital number, since it uses as much as digits as its factorization.

1128081991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38899408.

The product of its (nonzero) digits is 10368, while the sum is 40.

The square root of 1128081991 is about 33586.9318485628. The cubic root of 1128081991 is about 1040.9907936423.

The spelling of 1128081991 in words is "one billion, one hundred twenty-eight million, eighty-one thousand, nine hundred ninety-one".