20757 has 16 divisors (see below), whose sum is σ = 32832. Its totient is φ = 11520.

The previous prime is 20753. The next prime is 20759. The reversal of 20757 is 75702.

20757 is nontrivially palindromic in base 16.

It is not a de Polignac number, because 20757 - 2² = 20753 is a prime.

20757 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20753) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 543 + ... + 579.

It is an arithmetic number, because the mean of its divisors is an integer number (2052).

2²⁰⁷⁵⁷ is an apocalyptic number.

It is an amenable number.

20757 is a deficient number, since it is larger than the sum of its proper divisors (12075).

20757 is a wasteful number, since it uses less digits than its factorization.

20757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68.

The product of its (nonzero) digits is 490, while the sum is 21.

The square root of 20757 is about 144.0728982148. The cubic root of 20757 is about 27.4824129975.

Subtracting from 20757 its sum of digits (21), we obtain a 4-th power (20736 = 12⁴).

Subtracting 20757 from its reverse (75702), we obtain a palindrome (54945).

It can be divided in two parts, 20 and 757, that added together give a palindrome (777).

The spelling of 20757 in words is "twenty thousand, seven hundred fifty-seven".