205981 has 2 divisors, whose sum is σ = 205982. Its totient is φ = 205980.

The previous prime is 205967. The next prime is 205991. The reversal of 205981 is 189502.

205981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 202500 + 3481 = 450^2 + 59^2 .

It is a cyclic number.

It is not a de Polignac number, because 205981 - 2⁵ = 205949 is a prime.

It is a super-2 number, since 2×205981² = 84856344722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102990 + 102991.

It is an arithmetic number, because the mean of its divisors is an integer number (102991).

2²⁰⁵⁹⁸¹ is an apocalyptic number.

It is an amenable number.

205981 is a deficient number, since it is larger than the sum of its proper divisors (1).

205981 is an equidigital number, since it uses as much as digits as its factorization.

205981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 205981 is about 453.8512972329. The cubic root of 205981 is about 59.0575900382.

The spelling of 205981 in words is "two hundred five thousand, nine hundred eighty-one".