21012320123 has 4 divisors (see below), whose sum is σ = 21086568888. Its totient is φ = 20938071360.

The previous prime is 21012320117. The next prime is 21012320143. The reversal of 21012320123 is 32102321012.

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

It is a cyclic number.

It is not a de Polignac number, because 21012320123 - 2⁴ = 21012320107 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21012320143) 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, 37123958 + ... + 37124523.

It is an arithmetic number, because the mean of its divisors is an integer number (5271642222).

Almost surely, 2^21012320123 is an apocalyptic number.

21012320123 is a deficient number, since it is larger than the sum of its proper divisors (74248765).

21012320123 is an equidigital number, since it uses as much as digits as its factorization.

21012320123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74248764.

The product of its (nonzero) digits is 144, while the sum is 17.

Adding to 21012320123 its reverse (32102321012), we get a palindrome (53114641135).

The spelling of 21012320123 in words is "twenty-one billion, twelve million, three hundred twenty thousand, one hundred twenty-three".