991923 has 4 divisors (see below), whose sum is σ = 1322568. Its totient is φ = 661280.

The previous prime is 991909. The next prime is 991927. The reversal of 991923 is 329199.

991923 is nontrivially palindromic in base 8.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 991923 - 2¹⁸ = 729779 is a prime.

It is a super-2 number, since 2×991923² = 1967822475858, which contains 22 as substring.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (991927) 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 3 ways as a sum of consecutive naturals, for example, 165318 + ... + 165323.

It is an arithmetic number, because the mean of its divisors is an integer number (330642).

2⁹⁹¹⁹²³ is an apocalyptic number.

991923 is a deficient number, since it is larger than the sum of its proper divisors (330645).

991923 is a wasteful number, since it uses less digits than its factorization.

991923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330644.

The product of its digits is 4374, while the sum is 33.

The square root of 991923 is about 995.9533121588. The cubic root of 991923 is about 99.7300385305.

The spelling of 991923 in words is "nine hundred ninety-one thousand, nine hundred twenty-three".