123555581 has 2 divisors, whose sum is σ = 123555582. Its totient is φ = 123555580.

The previous prime is 123555569. The next prime is 123555583. The reversal of 123555581 is 185555321.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 101324356 + 22231225 = 10066^2 + 4715^2 .

It is a cyclic number.

It is not a de Polignac number, because 123555581 - 2²⁶ = 56446717 is a prime.

It is a super-2 number, since 2×123555581² = 30531963192495122, which contains 22 as substring.

Together with 123555583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123555583) 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, 61777790 + 61777791.

It is an arithmetic number, because the mean of its divisors is an integer number (61777791).

Almost surely, 2^123555581 is an apocalyptic number.

It is an amenable number.

123555581 is a deficient number, since it is larger than the sum of its proper divisors (1).

123555581 is an equidigital number, since it uses as much as digits as its factorization.

123555581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 30000, while the sum is 35.

The square root of 123555581 is about 11115.5558115643. Note that the first 3 decimals coincide. The cubic root of 123555581 is about 498.0666418884.

The spelling of 123555581 in words is "one hundred twenty-three million, five hundred fifty-five thousand, five hundred eighty-one".