123555661 has 2 divisors, whose sum is σ = 123555662. Its totient is φ = 123555660.

The previous prime is 123555659. The next prime is 123555713. The reversal of 123555661 is 166555321.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 116769636 + 6786025 = 10806^2 + 2605^2 .

It is a cyclic number.

It is not a de Polignac number, because 123555661 - 2¹ = 123555659 is a prime.

Together with 123555659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123555161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 61777830 + 61777831.

It is an arithmetic number, because the mean of its divisors is an integer number (61777831).

Almost surely, 2^123555661 is an apocalyptic number.

It is an amenable number.

123555661 is a deficient number, since it is larger than the sum of its proper divisors (1).

123555661 is an equidigital number, since it uses as much as digits as its factorization.

123555661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27000, while the sum is 34.

The square root of 123555661 is about 11115.5594101242. The cubic root of 123555661 is about 498.0667493847.

The spelling of 123555661 in words is "one hundred twenty-three million, five hundred fifty-five thousand, six hundred sixty-one".