991819 has 4 divisors (see below), whose sum is σ = 1044040. Its totient is φ = 939600.

The previous prime is 991817. The next prime is 991867. The reversal of 991819 is 918199.

991819 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 991819 - 2¹ = 991817 is a prime.

It is a super-2 number, since 2×991819² = 1967409857522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991811) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26082 + ... + 26119.

It is an arithmetic number, because the mean of its divisors is an integer number (261010).

2⁹⁹¹⁸¹⁹ is an apocalyptic number.

991819 is a deficient number, since it is larger than the sum of its proper divisors (52221).

991819 is a wasteful number, since it uses less digits than its factorization.

991819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52220.

The product of its digits is 5832, while the sum is 37.

The square root of 991819 is about 995.9010995074. The cubic root of 991819 is about 99.7265529487.

It can be divided in two parts, 99 and 1819, that multiplied together give a palindrome (180081).

The spelling of 991819 in words is "nine hundred ninety-one thousand, eight hundred nineteen".