991015 has 16 divisors (see below), whose sum is σ = 1283040. Its totient is φ = 732160.

The previous prime is 991009. The next prime is 991027. The reversal of 991015 is 510199.

991015 = 250² + 251² + ... + 264².

It is not a de Polignac number, because 991015 - 2⁷ = 990887 is a prime.

It is a super-2 number, since 2×991015² = 1964221460450, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 7500 + ... + 7630.

It is an arithmetic number, because the mean of its divisors is an integer number (80190).

2⁹⁹¹⁰¹⁵ is an apocalyptic number.

991015 is a deficient number, since it is larger than the sum of its proper divisors (292025).

991015 is a wasteful number, since it uses less digits than its factorization.

991015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242.

The product of its (nonzero) digits is 405, while the sum is 25.

The square root of 991015 is about 995.4973631306. The cubic root of 991015 is about 99.6995984930.

The spelling of 991015 in words is "nine hundred ninety-one thousand, fifteen".