1128856991 has 4 divisors (see below), whose sum is σ = 1143146400. Its totient is φ = 1114567584.

The previous prime is 1128856979. The next prime is 1128857039. The reversal of 1128856991 is 1996588211.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1996588211 = 5147 ⋅387913.

It is a cyclic number.

It is not a de Polignac number, because 1128856991 - 2¹⁴ = 1128840607 is a prime.

It is a super-2 number, since 2×1128856991² = 2548636212259148162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1128856921) 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, 7144586 + ... + 7144743.

It is an arithmetic number, because the mean of its divisors is an integer number (285786600).

Almost surely, 2^1128856991 is an apocalyptic number.

1128856991 is a deficient number, since it is larger than the sum of its proper divisors (14289409).

1128856991 is an equidigital number, since it uses as much as digits as its factorization.

1128856991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14289408.

The product of its digits is 311040, while the sum is 50.

The square root of 1128856991 is about 33598.4670930089. The cubic root of 1128856991 is about 1041.2291283232.

The spelling of 1128856991 in words is "one billion, one hundred twenty-eight million, eight hundred fifty-six thousand, nine hundred ninety-one".