991775 has 6 divisors (see below), whose sum is σ = 1229832. Its totient is φ = 793400.

The previous prime is 991751. The next prime is 991777. The reversal of 991775 is 577199.

It is not a de Polignac number, because 991775 - 2¹⁶ = 926239 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991777) 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, 19811 + ... + 19860.

It is an arithmetic number, because the mean of its divisors is an integer number (204972).

2⁹⁹¹⁷⁷⁵ is an apocalyptic number.

991775 is a deficient number, since it is larger than the sum of its proper divisors (238057).

991775 is a wasteful number, since it uses less digits than its factorization.

991775 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39681 (or 39676 counting only the distinct ones).

The product of its digits is 19845, while the sum is 38.

The square root of 991775 is about 995.8790087154. The cubic root of 991775 is about 99.7250782060.

The spelling of 991775 in words is "nine hundred ninety-one thousand, seven hundred seventy-five".