991523 has 6 divisors (see below), whose sum is σ = 1073844. Its totient is φ = 915096.

The previous prime is 991511. The next prime is 991531. The reversal of 991523 is 325199.

It is not a de Polignac number, because 991523 - 2¹⁶ = 925987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991223) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2765 + ... + 3102.

It is an arithmetic number, because the mean of its divisors is an integer number (178974).

2⁹⁹¹⁵²³ is an apocalyptic number.

991523 is a deficient number, since it is larger than the sum of its proper divisors (82321).

991523 is a wasteful number, since it uses less digits than its factorization.

991523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5893 (or 5880 counting only the distinct ones).

The product of its digits is 2430, while the sum is 29.

The square root of 991523 is about 995.7524792839. The cubic root of 991523 is about 99.7166311125.

The spelling of 991523 in words is "nine hundred ninety-one thousand, five hundred twenty-three".