991939 has 4 divisors (see below), whose sum is σ = 1068256. Its totient is φ = 915624.

The previous prime is 991931. The next prime is 991943. The reversal of 991939 is 939199.

991939 = 72² + 73² + ... + 149².

991939 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 991939 - 2³ = 991931 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991931) 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, 38139 + ... + 38164.

It is an arithmetic number, because the mean of its divisors is an integer number (267064).

2⁹⁹¹⁹³⁹ is an apocalyptic number.

991939 is a deficient number, since it is larger than the sum of its proper divisors (76317).

991939 is a wasteful number, since it uses less digits than its factorization.

991939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76316.

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

The square root of 991939 is about 995.9613446314. The cubic root of 991939 is about 99.7305747523.

The spelling of 991939 in words is "nine hundred ninety-one thousand, nine hundred thirty-nine".