21212121222021 has 4 divisors (see below), whose sum is σ = 28282828296032. Its totient is φ = 14141414148012.

The previous prime is 21212121221923. The next prime is 21212121222023. The reversal of 21212121222021 is 12022212121212.

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 21212121222021 - 2¹⁵ = 21212121189253 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212121222023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3535353537001 + ... + 3535353537006.

It is an arithmetic number, because the mean of its divisors is an integer number (7070707074008).

Almost surely, 2^{21212121222021} is an apocalyptic number.

It is an amenable number.

21212121222021 is a deficient number, since it is larger than the sum of its proper divisors (7070707074011).

21212121222021 is an equidigital number, since it uses as much as digits as its factorization.

21212121222021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7070707074010.

The product of its (nonzero) digits is 256, while the sum is 21.

Adding to 21212121222021 its reverse (12022212121212), we get a palindrome (33234333343233).

The spelling of 21212121222021 in words is "twenty-one trillion, two hundred twelve billion, one hundred twenty-one million, two hundred twenty-two thousand, twenty-one".