123581 has 2 divisors, whose sum is σ = 123582. Its totient is φ = 123580.

The previous prime is 123553. The next prime is 123583. The reversal of 123581 is 185321.

123581 is nontrivially palindromic in base 3.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 105625 + 17956 = 325^2 + 134^2 .

It is a cyclic number.

It is not a de Polignac number, because 123581 - 2⁶ = 123517 is a prime.

It is a super-2 number, since 2×123581² = 30544527122, which contains 22 as substring.

Together with 123583, it forms a pair of twin primes.

It is a Chen prime.

It is a nialpdrome in base 13.

It is a zygodrome in base 13.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123583) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 61790 + 61791.

It is an arithmetic number, because the mean of its divisors is an integer number (61791).

2¹²³⁵⁸¹ is an apocalyptic number.

It is an amenable number.

123581 is a deficient number, since it is larger than the sum of its proper divisors (1).

123581 is an equidigital number, since it uses as much as digits as its factorization.

123581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 240, while the sum is 20.

The square root of 123581 is about 351.5408937805. The cubic root of 123581 is about 49.8100795176.

The spelling of 123581 in words is "one hundred twenty-three thousand, five hundred eighty-one".