123128043021 has 24 divisors (see below), whose sum is σ = 178981928736. Its totient is φ = 81563902560.

The previous prime is 123128042971. The next prime is 123128043079. The reversal of 123128043021 is 120340821321.

123128043021 is a `hidden beast` number, since 123 + 12 + 80 + 430 + 21 = 666.

It is not a de Polignac number, because 123128043021 - 2⁷ = 123128042893 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (123128043421) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12380911 + ... + 12390851.

It is an arithmetic number, because the mean of its divisors is an integer number (7457580364).

Almost surely, 2^123128043021 is an apocalyptic number.

It is an amenable number.

123128043021 is a deficient number, since it is larger than the sum of its proper divisors (55853885715).

123128043021 is a wasteful number, since it uses less digits than its factorization.

123128043021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18553 (or 18550 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

Adding to 123128043021 its reverse (120340821321), we get a palindrome (243468864342).

The spelling of 123128043021 in words is "one hundred twenty-three billion, one hundred twenty-eight million, forty-three thousand, twenty-one".