20569 has 4 divisors (see below), whose sum is σ = 20944.
Its totient is φ = 20196.
The previous prime is 20563. The next prime is 20593. The reversal of 20569 is 96502.
It is a semiprime because it is the product of two primes.
It is a cyclic number.
It is not a de Polignac number, because 20569 - 27 = 20441 is a prime.
It is a super-2 number, since 2×205692 = 846167522, which contains 22 as substring.
It is a tetranacci number.
It is a Duffinian number.
It is a plaindrome in base 11.
It is a nialpdrome in base 12.
It is not an unprimeable number, because it can be changed into a prime (20563) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 87 + ... + 220.
It is an arithmetic number, because the mean of its divisors is an integer number (5236).
220569 is an apocalyptic number.
It is an amenable number.
20569 is a deficient number, since it is larger than the sum of its proper divisors (375).
20569 is an equidigital number, since it uses as much as digits as its factorization.
20569 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 374.
The product of its (nonzero) digits is 540, while the sum is 22.
The square root of 20569 is about 143.4189666676.
The cubic root of 20569 is about 27.3991901300.
The spelling of 20569 in words is "twenty thousand, five hundred sixty-nine".