123331561 has 4 divisors (see below), whose sum is σ = 124892800. Its totient is φ = 121770324.

The previous prime is 123331541. The next prime is 123331573. The reversal of 123331561 is 165133321.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 165133321 = 2131 ⋅77491.

It is a cyclic number.

It is not a de Polignac number, because 123331561 - 2⁷ = 123331433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (123331511) 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 in 3 ways as a sum of consecutive naturals, for example, 780501 + ... + 780658.

It is an arithmetic number, because the mean of its divisors is an integer number (31223200).

Almost surely, 2^123331561 is an apocalyptic number.

It is an amenable number.

123331561 is a deficient number, since it is larger than the sum of its proper divisors (1561239).

123331561 is an equidigital number, since it uses as much as digits as its factorization.

123331561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1561238.

The product of its digits is 1620, while the sum is 25.

The square root of 123331561 is about 11105.4743707777. The cubic root of 123331561 is about 497.7654430541.

Adding to 123331561 its reverse (165133321), we get a palindrome (288464882).

The spelling of 123331561 in words is "one hundred twenty-three million, three hundred thirty-one thousand, five hundred sixty-one".