990391 has 4 divisors (see below), whose sum is σ = 1004032. Its totient is φ = 976752.

The previous prime is 990389. The next prime is 990397. The reversal of 990391 is 193099.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 193099 = 31 ⋅6229.

It is a cyclic number.

It is not a de Polignac number, because 990391 - 2¹ = 990389 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 (990397) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6711 + ... + 6856.

It is an arithmetic number, because the mean of its divisors is an integer number (251008).

2⁹⁹⁰³⁹¹ is an apocalyptic number.

990391 is a deficient number, since it is larger than the sum of its proper divisors (13641).

990391 is a wasteful number, since it uses less digits than its factorization.

990391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13640.

The product of its (nonzero) digits is 2187, while the sum is 31.

The square root of 990391 is about 995.1839026029. The cubic root of 990391 is about 99.6786685671.

The spelling of 990391 in words is "nine hundred ninety thousand, three hundred ninety-one".