243655556381 has 2 divisors, whose sum is σ = 243655556382. Its totient is φ = 243655556380.

The previous prime is 243655556323. The next prime is 243655556401. The reversal of 243655556381 is 183655556342.

243655556381 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., 195394057156 + 48261499225 = 442034^2 + 219685^2 .

It is a cyclic number.

It is not a de Polignac number, because 243655556381 - 2¹⁰ = 243655555357 is a prime.

It is a super-2 number, since 2×243655556381² (a number of 24 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243655550381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121827778190 + 121827778191.

It is an arithmetic number, because the mean of its divisors is an integer number (121827778191).

Almost surely, 2^243655556381 is an apocalyptic number.

It is an amenable number.

243655556381 is a deficient number, since it is larger than the sum of its proper divisors (1).

243655556381 is an equidigital number, since it uses as much as digits as its factorization.

243655556381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12960000, while the sum is 53.

The spelling of 243655556381 in words is "two hundred forty-three billion, six hundred fifty-five million, five hundred fifty-six thousand, three hundred eighty-one".