21420120121 has 4 divisors (see below), whose sum is σ = 21431820544. Its totient is φ = 21408419700.

The previous prime is 21420120109. The next prime is 21420120203. The reversal of 21420120121 is 12102102412.

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 not a de Polignac number, because 21420120121 - 2¹³ = 21420111929 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21420120095 and 21420120104.

It is not an unprimeable number, because it can be changed into a prime (21420120221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5847465 + ... + 5851126.

It is an arithmetic number, because the mean of its divisors is an integer number (5357955136).

Almost surely, 2^21420120121 is an apocalyptic number.

It is an amenable number.

21420120121 is a deficient number, since it is larger than the sum of its proper divisors (11700423).

21420120121 is a wasteful number, since it uses less digits than its factorization.

21420120121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11700422.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21420120121 its reverse (12102102412), we get a palindrome (33522222533).

The spelling of 21420120121 in words is "twenty-one billion, four hundred twenty million, one hundred twenty thousand, one hundred twenty-one".