991958 has 12 divisors (see below), whose sum is σ = 1635900. Its totient is φ = 450780.

The previous prime is 991957. The next prime is 991961. The reversal of 991958 is 859199.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1808 + ... + 2291.

It is an arithmetic number, because the mean of its divisors is an integer number (136325).

2⁹⁹¹⁹⁵⁸ is an apocalyptic number.

991958 is a deficient number, since it is larger than the sum of its proper divisors (643942).

991958 is a wasteful number, since it uses less digits than its factorization.

991958 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4123 (or 4112 counting only the distinct ones).

The product of its digits is 29160, while the sum is 41.

The square root of 991958 is about 995.9708831085. The cubic root of 991958 is about 99.7312115081.

The spelling of 991958 in words is "nine hundred ninety-one thousand, nine hundred fifty-eight".