20897 has 2 divisors, whose sum is σ = 20898. Its totient is φ = 20896.

The previous prime is 20887. The next prime is 20899. The reversal of 20897 is 79802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18496 + 2401 = 136^2 + 49^2 .

It is a cyclic number.

It is not a de Polignac number, because 20897 - 2⁸ = 20641 is a prime.

Together with 20899, it forms a pair of twin primes.

It is a Chen prime.

It is a plaindrome in base 11 and base 14.

It is not a weakly prime, because it can be changed into another prime (20899) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10448 + 10449.

It is an arithmetic number, because the mean of its divisors is an integer number (10449).

2²⁰⁸⁹⁷ is an apocalyptic number.

It is an amenable number.

20897 is a deficient number, since it is larger than the sum of its proper divisors (1).

20897 is an equidigital number, since it uses as much as digits as its factorization.

20897 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 20897 is about 144.5579468587. The cubic root of 20897 is about 27.5440615965.

The spelling of 20897 in words is "twenty thousand, eight hundred ninety-seven".