991239 has 4 divisors (see below), whose sum is σ = 1321656. Its totient is φ = 660824.

The previous prime is 991229. The next prime is 991261. The reversal of 991239 is 932199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 932199 = 3 ⋅310733.

It is a cyclic number.

It is not a de Polignac number, because 991239 - 2⁴ = 991223 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991229) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 165204 + ... + 165209.

It is an arithmetic number, because the mean of its divisors is an integer number (330414).

2⁹⁹¹²³⁹ is an apocalyptic number.

991239 is a deficient number, since it is larger than the sum of its proper divisors (330417).

991239 is a wasteful number, since it uses less digits than its factorization.

991239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330416.

The product of its digits is 4374, while the sum is 33.

The square root of 991239 is about 995.6098633501. The cubic root of 991239 is about 99.7071096567.

The spelling of 991239 in words is "nine hundred ninety-one thousand, two hundred thirty-nine".