789991 has 4 divisors (see below), whose sum is σ = 791800. Its totient is φ = 788184.

The previous prime is 789979. The next prime is 790003. The reversal of 789991 is 199987.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199987 = 227 ⋅881.

It is an interprime number because it is at equal distance from previous prime (789979) and next prime (790003).

It is a cyclic number.

It is not a de Polignac number, because 789991 - 2⁵ = 789959 is a prime.

It is an Ulam number.

It is a Duffinian number.

789991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (789941) 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, 205 + ... + 1273.

It is an arithmetic number, because the mean of its divisors is an integer number (197950).

2⁷⁸⁹⁹⁹¹ is an apocalyptic number.

789991 is a deficient number, since it is larger than the sum of its proper divisors (1809).

789991 is a wasteful number, since it uses less digits than its factorization.

789991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1808.

The product of its digits is 40824, while the sum is 43.

The square root of 789991 is about 888.8143788216. The cubic root of 789991 is about 92.4430036017.

It can be divided in two parts, 7 and 89991, that added together give a palindrome (89998).

The spelling of 789991 in words is "seven hundred eighty-nine thousand, nine hundred ninety-one".