20505 has 8 divisors (see below), whose sum is σ = 32832. Its totient is φ = 10928.

The previous prime is 20483. The next prime is 20507. The reversal of 20505 is 50502.

20505 is nontrivially palindromic in base 9.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20505 - 2⁶ = 20441 is a prime.

It is a Curzon number.

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (20507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 669 + ... + 698.

It is an arithmetic number, because the mean of its divisors is an integer number (4104).

2²⁰⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

20505 is a deficient number, since it is larger than the sum of its proper divisors (12327).

20505 is a wasteful number, since it uses less digits than its factorization.

20505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1375.

The product of its (nonzero) digits is 50, while the sum is 12.

The square root of 20505 is about 143.1956703256. The cubic root of 20505 is about 27.3707432759.

It can be divided in two parts, 20 and 505, that added together give a palindrome (525).

The spelling of 20505 in words is "twenty thousand, five hundred five".