20657 has 8 divisors (see below), whose sum is σ = 25536. Its totient is φ = 16272.

The previous prime is 20641. The next prime is 20663. The reversal of 20657 is 75602.

20657 = 8⁴ + 9⁴ + 10⁴.

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 20657 - 2⁴ = 20641 is a prime.

It is a plaindrome in base 11.

It is a nialpdrome in base 12 and base 13.

It is a zygodrome in base 12.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 20657.

It is not an unprimeable number, because it can be changed into a prime (20627) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23 + ... + 204.

It is an arithmetic number, because the mean of its divisors is an integer number (3192).

2²⁰⁶⁵⁷ is an apocalyptic number.

It is an amenable number.

20657 is a deficient number, since it is larger than the sum of its proper divisors (4879).

20657 is a wasteful number, since it uses less digits than its factorization.

20657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 20657 is about 143.7254326833. The cubic root of 20657 is about 27.4382083676.

Subtracting 20657 from its reverse (75602), we obtain a palindrome (54945).

The spelling of 20657 in words is "twenty thousand, six hundred fifty-seven".