1098991 has 4 divisors (see below), whose sum is σ = 1103184. Its totient is φ = 1094800.

The previous prime is 1098989. The next prime is 1099031. The reversal of 1098991 is 1998901.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1998901 = 193 ⋅10357.

It is a cyclic number.

It is not a de Polignac number, because 1098991 - 2¹ = 1098989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1098991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1098191) 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, 1675 + ... + 2236.

It is an arithmetic number, because the mean of its divisors is an integer number (275796).

2^1098991 is an apocalyptic number.

1098991 is a deficient number, since it is larger than the sum of its proper divisors (4193).

1098991 is an equidigital number, since it uses as much as digits as its factorization.

1098991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4192.

The product of its (nonzero) digits is 5832, while the sum is 37.

The square root of 1098991 is about 1048.3277159362. The cubic root of 1098991 is about 103.1964391436.

It can be divided in two parts, 10989 and 91, that multiplied together give a palindrome (999999).

The spelling of 1098991 in words is "one million, ninety-eight thousand, nine hundred ninety-one".