20517 has 8 divisors (see below), whose sum is σ = 31296. Its totient is φ = 11712.

The previous prime is 20509. The next prime is 20521. The reversal of 20517 is 71502.

It is a happy number.

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

It is not a de Polignac number, because 20517 - 2³ = 20509 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20496 and 20505.

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 20517.

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, 468 + ... + 509.

It is an arithmetic number, because the mean of its divisors is an integer number (3912).

2²⁰⁵¹⁷ is an apocalyptic number.

It is an amenable number.

20517 is a deficient number, since it is larger than the sum of its proper divisors (10779).

20517 is an equidigital number, since it uses as much as digits as its factorization.

20517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 987.

The product of its (nonzero) digits is 70, while the sum is 15.

The square root of 20517 is about 143.2375649053. The cubic root of 20517 is about 27.3760815652.

Subtracting from 20517 its sum of digits (15), we obtain a palindrome (20502).

It can be divided in two parts, 205 and 17, that added together give a palindrome (222).

The spelling of 20517 in words is "twenty thousand, five hundred seventeen".