21210020121 has 4 divisors (see below), whose sum is σ = 28280026832. Its totient is φ = 14140013412.

The previous prime is 21210020053. The next prime is 21210020129. The reversal of 21210020121 is 12102001212.

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 not a de Polignac number, because 21210020121 - 2⁷ = 21210019993 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210020097 and 21210020106.

It is not an unprimeable number, because it can be changed into a prime (21210020129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3535003351 + ... + 3535003356.

It is an arithmetic number, because the mean of its divisors is an integer number (7070006708).

Almost surely, 2^21210020121 is an apocalyptic number.

It is an amenable number.

21210020121 is a deficient number, since it is larger than the sum of its proper divisors (7070006711).

21210020121 is an equidigital number, since it uses as much as digits as its factorization.

21210020121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7070006710.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21210020121 its reverse (12102001212), we get a palindrome (33312021333).

It can be divided in two parts, 212100 and 20121, that added together give a triangular number (232221 = T₆₈₁).

The spelling of 21210020121 in words is "twenty-one billion, two hundred ten million, twenty thousand, one hundred twenty-one".