19959 has 4 divisors (see below), whose sum is σ = 26616. Its totient is φ = 13304.

The previous prime is 19949. The next prime is 19961. The reversal of 19959 is 95991.

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 19959 - 2⁵ = 19927 is a prime.

It is an Ulam number.

It is a D-number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 19959.

It is not an unprimeable number, because it can be changed into a prime (19919) 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, 3324 + ... + 3329.

It is an arithmetic number, because the mean of its divisors is an integer number (6654).

2¹⁹⁹⁵⁹ is an apocalyptic number.

19959 is a deficient number, since it is larger than the sum of its proper divisors (6657).

19959 is an equidigital number, since it uses as much as digits as its factorization.

19959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6656.

The product of its digits is 3645, while the sum is 33.

The square root of 19959 is about 141.2763249805. The cubic root of 19959 is about 27.1256149563.

It can be divided in two parts, 1995 and 9, that multiplied together give a triangular number (17955 = T₁₈₉).

The spelling of 19959 in words is "nineteen thousand, nine hundred fifty-nine".