123138685661 has 2 divisors, whose sum is σ = 123138685662. Its totient is φ = 123138685660.

The previous prime is 123138685619. The next prime is 123138685667. The reversal of 123138685661 is 166586831321.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80343902500 + 42794783161 = 283450^2 + 206869^2 .

It is a cyclic number.

It is not a de Polignac number, because 123138685661 - 2¹⁸ = 123138423517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123138685667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 61569342830 + 61569342831.

It is an arithmetic number, because the mean of its divisors is an integer number (61569342831).

Almost surely, 2^123138685661 is an apocalyptic number.

It is an amenable number.

123138685661 is a deficient number, since it is larger than the sum of its proper divisors (1).

123138685661 is an equidigital number, since it uses as much as digits as its factorization.

123138685661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1244160, while the sum is 50.

The spelling of 123138685661 in words is "one hundred twenty-three billion, one hundred thirty-eight million, six hundred eighty-five thousand, six hundred sixty-one".