21123420121 has 4 divisors (see below), whose sum is σ = 21168652752. Its totient is φ = 21078187492.

The previous prime is 21123420103. The next prime is 21123420127. The reversal of 21123420121 is 12102432112.

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 21123420121 - 2⁹ = 21123419609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21123420127) 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, 22615615 + ... + 22616548.

It is an arithmetic number, because the mean of its divisors is an integer number (5292163188).

Almost surely, 2^21123420121 is an apocalyptic number.

It is an amenable number.

21123420121 is a deficient number, since it is larger than the sum of its proper divisors (45232631).

21123420121 is an equidigital number, since it uses as much as digits as its factorization.

21123420121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45232630.

The product of its (nonzero) digits is 192, while the sum is 19.

Adding to 21123420121 its reverse (12102432112), we get a palindrome (33225852233).

The spelling of 21123420121 in words is "twenty-one billion, one hundred twenty-three million, four hundred twenty thousand, one hundred twenty-one".