991005 has 8 divisors (see below), whose sum is σ = 1585632. Its totient is φ = 528528.

The previous prime is 990989. The next prime is 991009. The reversal of 991005 is 500199.

It is a happy number.

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

It is not a de Polignac number, because 991005 - 2⁴ = 990989 is a prime.

It is a Curzon number.

991005 is a lucky 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 pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33019 + ... + 33048.

It is an arithmetic number, because the mean of its divisors is an integer number (198204).

2⁹⁹¹⁰⁰⁵ is an apocalyptic number.

It is an amenable number.

991005 is a deficient number, since it is larger than the sum of its proper divisors (594627).

991005 is a wasteful number, since it uses less digits than its factorization.

991005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66075.

The product of its (nonzero) digits is 405, while the sum is 24.

The square root of 991005 is about 995.4923405029. The cubic root of 991005 is about 99.6992631468.

The spelling of 991005 in words is "nine hundred ninety-one thousand, five".