20849 has 2 divisors, whose sum is σ = 20850. Its totient is φ = 20848.

The previous prime is 20809. The next prime is 20857. The reversal of 20849 is 94802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20449 + 400 = 143^2 + 20^2 .

It is a cyclic number.

It is not a de Polignac number, because 20849 - 2⁸ = 20593 is a prime.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (20809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10424 + 10425.

It is an arithmetic number, because the mean of its divisors is an integer number (10425).

2²⁰⁸⁴⁹ is an apocalyptic number.

It is an amenable number.

20849 is a deficient number, since it is larger than the sum of its proper divisors (1).

20849 is an equidigital number, since it uses as much as digits as its factorization.

20849 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 20849 is about 144.3918280236. The cubic root of 20849 is about 27.5229560384.

The spelling of 20849 in words is "twenty thousand, eight hundred forty-nine".