20538 has 24 divisors (see below), whose sum is σ = 51168. Its totient is φ = 5832.

The previous prime is 20533. The next prime is 20543. The reversal of 20538 is 83502.

It is an interprime number because it is at equal distance from previous prime (20533) and next prime (20543).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a Curzon number.

It is a nialpdrome in base 12.

It is a self number, because there is not a number n which added to its sum of digits gives 20538.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20533) by changing a digit.

20538 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 45 + ... + 207.

It is an arithmetic number, because the mean of its divisors is an integer number (2132).

2²⁰⁵³⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20538, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25584).

20538 is an abundant number, since it is smaller than the sum of its proper divisors (30630).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20538 is a wasteful number, since it uses less digits than its factorization.

20538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178 (or 175 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 20538 is about 143.3108509500. The cubic root of 20538 is about 27.3854185651.

It can be divided in two parts, 205 and 38, that added together give a 5-th power (243 = 3⁵).

The spelling of 20538 in words is "twenty thousand, five hundred thirty-eight".