243781 has 2 divisors, whose sum is σ = 243782. Its totient is φ = 243780.

The previous prime is 243769. The next prime is 243787. The reversal of 243781 is 187342.

243781 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., 216225 + 27556 = 465^2 + 166^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-243781 is a prime.

It is a super-2 number, since 2×243781² = 118858351922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121890 + 121891.

It is an arithmetic number, because the mean of its divisors is an integer number (121891).

2²⁴³⁷⁸¹ is an apocalyptic number.

It is an amenable number.

243781 is a deficient number, since it is larger than the sum of its proper divisors (1).

243781 is an equidigital number, since it uses as much as digits as its factorization.

243781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1344, while the sum is 25.

The square root of 243781 is about 493.7418353755. The cubic root of 243781 is about 62.4692969196.

It can be divided in two parts, 243 and 781, that added together give a 10-th power (1024 = 2¹⁰).

The spelling of 243781 in words is "two hundred forty-three thousand, seven hundred eighty-one".