999391 has 4 divisors (see below), whose sum is σ = 1009792. Its totient is φ = 988992.

The previous prime is 999389. The next prime is 999431. The reversal of 999391 is 193999.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 193999 = 13 ⋅14923.

It is a cyclic number.

It is not a de Polignac number, because 999391 - 2¹ = 999389 is a prime.

It is a Duffinian number.

999391 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999331) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5055 + ... + 5248.

It is an arithmetic number, because the mean of its divisors is an integer number (252448).

2⁹⁹⁹³⁹¹ is an apocalyptic number.

999391 is a deficient number, since it is larger than the sum of its proper divisors (10401).

999391 is a wasteful number, since it uses less digits than its factorization.

999391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10400.

The product of its digits is 19683, while the sum is 40.

The square root of 999391 is about 999.6954536258. The cubic root of 999391 is about 99.9796958777.

The spelling of 999391 in words is "nine hundred ninety-nine thousand, three hundred ninety-one".