20542 has 4 divisors (see below), whose sum is σ = 30816. Its totient is φ = 10270.

The previous prime is 20533. The next prime is 20543. The reversal of 20542 is 24502.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 24502 = 2 ⋅12251.

It is a Smith number, since the sum of its digits (13) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20543) by changing a digit.

20542 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 5134 + ... + 5137.

It is an arithmetic number, because the mean of its divisors is an integer number (7704).

2²⁰⁵⁴² is an apocalyptic number.

20542 is a deficient number, since it is larger than the sum of its proper divisors (10274).

20542 is a wasteful number, since it uses less digits than its factorization.

20542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10273.

The product of its (nonzero) digits is 80, while the sum is 13.

The square root of 20542 is about 143.3248059479. The cubic root of 20542 is about 27.3871963196.

The spelling of 20542 in words is "twenty thousand, five hundred forty-two".