21213210121 has 4 divisors (see below), whose sum is σ = 21270082372. Its totient is φ = 21156337872.

The previous prime is 21213210103. The next prime is 21213210143. The reversal of 21213210121 is 12101231212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 6330430096 + 14882780025 = 79564^2 + 121995^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213210121 - 2²³ = 21204821513 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21213210095 and 21213210104.

It is not an unprimeable number, because it can be changed into a prime (21213210101) 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, 28435566 + ... + 28436311.

It is an arithmetic number, because the mean of its divisors is an integer number (5317520593).

Almost surely, 2^21213210121 is an apocalyptic number.

It is an amenable number.

21213210121 is a deficient number, since it is larger than the sum of its proper divisors (56872251).

21213210121 is an equidigital number, since it uses as much as digits as its factorization.

21213210121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56872250.

The product of its (nonzero) digits is 48, while the sum is 16.

Adding to 21213210121 its reverse (12101231212), we get a palindrome (33314441333).

The spelling of 21213210121 in words is "twenty-one billion, two hundred thirteen million, two hundred ten thousand, one hundred twenty-one".