204781 has 2 divisors, whose sum is σ = 204782. Its totient is φ = 204780.

The previous prime is 204751. The next prime is 204791. The reversal of 204781 is 187402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 184900 + 19881 = 430^2 + 141^2 .

It is a cyclic number.

It is not a de Polignac number, because 204781 - 2⁵ = 204749 is a prime.

It is a super-2 number, since 2×204781² = 83870515922, which contains 22 as substring.

It is a Chen prime.

It is an Ulam number.

It is equal to p₁₈₃₆₄ and since 204781 and 18364 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (204751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102390 + 102391.

It is an arithmetic number, because the mean of its divisors is an integer number (102391).

2²⁰⁴⁷⁸¹ is an apocalyptic number.

It is an amenable number.

204781 is a deficient number, since it is larger than the sum of its proper divisors (1).

204781 is an equidigital number, since it uses as much as digits as its factorization.

204781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 204781 is about 452.5273472399. The cubic root of 204781 is about 58.9426810938.

The spelling of 204781 in words is "two hundred four thousand, seven hundred eighty-one".