1231561205123 has 2 divisors, whose sum is σ = 1231561205124. Its totient is φ = 1231561205122.

The previous prime is 1231561205117. The next prime is 1231561205131. The reversal of 1231561205123 is 3215021651321.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1231561205123 - 2⁶ = 1231561205059 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1231561205123.

It is not a weakly prime, because it can be changed into another prime (1231561205183) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 615780602561 + 615780602562.

It is an arithmetic number, because the mean of its divisors is an integer number (615780602562).

Almost surely, 2^{1231561205123} is an apocalyptic number.

1231561205123 is a deficient number, since it is larger than the sum of its proper divisors (1).

1231561205123 is an equidigital number, since it uses as much as digits as its factorization.

1231561205123 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10800, while the sum is 32.

Adding to 1231561205123 its reverse (3215021651321), we get a palindrome (4446582856444).

The spelling of 1231561205123 in words is "one trillion, two hundred thirty-one billion, five hundred sixty-one million, two hundred five thousand, one hundred twenty-three".