20123123521 has 4 divisors (see below), whose sum is σ = 20209489092. Its totient is φ = 20036757952.

The previous prime is 20123123483. The next prime is 20123123543. The reversal of 20123123521 is 12532132102.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8665561921 + 11457561600 = 93089^2 + 107040^2 .

It is a cyclic number.

It is not a de Polignac number, because 20123123521 - 2¹⁵ = 20123090753 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20123123492 and 20123123501.

It is not an unprimeable number, because it can be changed into a prime (20123123551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 43182436 + ... + 43182901.

It is an arithmetic number, because the mean of its divisors is an integer number (5052372273).

Almost surely, 2^20123123521 is an apocalyptic number.

It is an amenable number.

20123123521 is a deficient number, since it is larger than the sum of its proper divisors (86365571).

20123123521 is an equidigital number, since it uses as much as digits as its factorization.

20123123521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86365570.

The product of its (nonzero) digits is 720, while the sum is 22.

Adding to 20123123521 its reverse (12532132102), we get a palindrome (32655255623).

The spelling of 20123123521 in words is "twenty billion, one hundred twenty-three million, one hundred twenty-three thousand, five hundred twenty-one".