20571 has 4 divisors (see below), whose sum is σ = 27432. Its totient is φ = 13712.

The previous prime is 20563. The next prime is 20593. The reversal of 20571 is 17502.

It is a happy number.

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 20571 - 2³ = 20563 is a prime.

It is a D-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 20571.

It is not an unprimeable number, because it can be changed into a prime (20521) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 3426 + ... + 3431.

It is an arithmetic number, because the mean of its divisors is an integer number (6858).

2²⁰⁵⁷¹ is an apocalyptic number.

20571 is a deficient number, since it is larger than the sum of its proper divisors (6861).

20571 is an equidigital number, since it uses as much as digits as its factorization.

20571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6860.

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

The square root of 20571 is about 143.4259390766. The cubic root of 20571 is about 27.4000781428.

It can be divided in two parts, 205 and 71, that added together give a triangular number (276 = T₂₃).

The spelling of 20571 in words is "twenty thousand, five hundred seventy-one".