991309 has 8 divisors (see below), whose sum is σ = 1088928. Its totient is φ = 894960.

The previous prime is 991273. The next prime is 991313. The reversal of 991309 is 903199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 991309 - 2⁷ = 991181 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 (991009) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2299 + ... + 2695.

It is an arithmetic number, because the mean of its divisors is an integer number (136116).

2⁹⁹¹³⁰⁹ is an apocalyptic number.

It is an amenable number.

991309 is a deficient number, since it is larger than the sum of its proper divisors (97619).

991309 is a wasteful number, since it uses less digits than its factorization.

991309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 635.

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

The square root of 991309 is about 995.6450170618. The cubic root of 991309 is about 99.7094566632.

The spelling of 991309 in words is "nine hundred ninety-one thousand, three hundred nine".