19858 has 4 divisors (see below), whose sum is σ = 29790. Its totient is φ = 9928.

The previous prime is 19853. The next prime is 19861. The reversal of 19858 is 85891.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 85891 = 13 ⋅6607.

It can be written as a sum of positive squares in only one way, i.e., 18769 + 1089 = 137^2 + 33^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (19853) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4963 + ... + 4966.

2¹⁹⁸⁵⁸ is an apocalyptic number.

19858 is a deficient number, since it is larger than the sum of its proper divisors (9932).

19858 is an equidigital number, since it uses as much as digits as its factorization.

19858 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9931.

The product of its digits is 2880, while the sum is 31.

The square root of 19858 is about 140.9184161137. The cubic root of 19858 is about 27.0797823089.

It can be divided in two parts, 198 and 58, that added together give a 8-th power (256 = 2⁸).

The spelling of 19858 in words is "nineteen thousand, eight hundred fifty-eight".