205 has 4 divisors (see below), whose sum is σ = 252. Its totient is φ = 160.

The previous prime is 199. The next prime is 211. The reversal of 205 is 502.

Adding to 205 its reverse (502), we get a palindrome (707).

It can be divided in two parts, 20 and 5, that multiplied together give a square (100 = 10^{2}).

205 is nontrivially palindromic in base 12.

205 is an esthetic number in base 16, because in such base its adjacent digits differ by 1.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 502 = 2 ⋅251.

It is an interprime number because it is at equal distance from previous prime (199) and next prime (211).

It can be written as a sum of positive squares in 2 ways, for example, as 36 + 169 = 6^2 + 13^2 .

It is a sliding number, since 205 = 5 + 200 and 1/5 + 1/200 = 0.205.

It is not a de Polignac number, because 205 - 2^{3} = 197 is a prime.

It is a Duffinian number.

205 is an undulating number in base 12.

205 is a lucky number.

It is a plaindrome in base 9, base 11, base 13 and base 16.

It is a nialpdrome in base 6 and base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (5) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16 + ... + 25.

It is an arithmetic number, because the mean of its divisors is an integer number (63).

It is an amenable number.

205 is a deficient number, since it is larger than the sum of its proper divisors (47).

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

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

The sum of its prime factors is 46.

The product of its (nonzero) digits is 10, while the sum is 7.

The square root of 205 is about 14.3178210633. The cubic root of 205 is about 5.8963685400.

The spelling of 205 in words is "two hundred five", and thus it is an aban number.

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