21423220121 has 4 divisors (see below), whose sum is σ = 21423759744. Its totient is φ = 21422680500.

The previous prime is 21423220109. The next prime is 21423220151. The reversal of 21423220121 is 12102232412.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21423220121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21423220093 and 21423220102.

It is not an unprimeable number, because it can be changed into a prime (21423220151) 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, 205085 + ... + 291386.

It is an arithmetic number, because the mean of its divisors is an integer number (5355939936).

Almost surely, 2^21423220121 is an apocalyptic number.

It is an amenable number.

21423220121 is a deficient number, since it is larger than the sum of its proper divisors (539623).

21423220121 is an equidigital number, since it uses as much as digits as its factorization.

21423220121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 539622.

The product of its (nonzero) digits is 384, while the sum is 20.

Adding to 21423220121 its reverse (12102232412), we get a palindrome (33525452533).

The spelling of 21423220121 in words is "twenty-one billion, four hundred twenty-three million, two hundred twenty thousand, one hundred twenty-one".