21210212202121 has 4 divisors (see below), whose sum is σ = 21350677183744. Its totient is φ = 21069747220500.

The previous prime is 21210212202097. The next prime is 21210212202139. The reversal of 21210212202121 is 12120221201212.

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 21210212202121 - 2⁷ = 21210212201993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21210212202161) 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, 70232490585 + ... + 70232490886.

It is an arithmetic number, because the mean of its divisors is an integer number (5337669295936).

Almost surely, 2^{21210212202121} is an apocalyptic number.

It is an amenable number.

21210212202121 is a deficient number, since it is larger than the sum of its proper divisors (140464981623).

21210212202121 is a wasteful number, since it uses less digits than its factorization.

21210212202121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140464981622.

The product of its (nonzero) digits is 128, while the sum is 19.

Adding to 21210212202121 its reverse (12120221201212), we get a palindrome (33330433403333).

The spelling of 21210212202121 in words is "twenty-one trillion, two hundred ten billion, two hundred twelve million, two hundred two thousand, one hundred twenty-one".