555991 has 4 divisors (see below), whose sum is σ = 557512. Its totient is φ = 554472.

The previous prime is 555967. The next prime is 556007. The reversal of 555991 is 199555.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-555991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (555931) 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 3 ways as a sum of consecutive naturals, for example, 160 + ... + 1066.

It is an arithmetic number, because the mean of its divisors is an integer number (139378).

2⁵⁵⁵⁹⁹¹ is an apocalyptic number.

555991 is the 431-st hex number.

555991 is a deficient number, since it is larger than the sum of its proper divisors (1521).

555991 is an equidigital number, since it uses as much as digits as its factorization.

555991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1520.

The product of its digits is 10125, while the sum is 34.

The square root of 555991 is about 745.6480402978. The cubic root of 555991 is about 82.2285415022.

The spelling of 555991 in words is "five hundred fifty-five thousand, nine hundred ninety-one".