21012212122221 has 4 divisors (see below), whose sum is σ = 28016282829632. Its totient is φ = 14008141414812.

The previous prime is 21012212122199. The next prime is 21012212122261. The reversal of 21012212122221 is 12222121221012.

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 21012212122221 - 2¹⁴ = 21012212105837 is a prime.

It is a super-2 number, since 2×21012212122221² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012212122261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3502035353701 + ... + 3502035353706.

It is an arithmetic number, because the mean of its divisors is an integer number (7004070707408).

Almost surely, 2^{21012212122221} is an apocalyptic number.

It is an amenable number.

21012212122221 is a deficient number, since it is larger than the sum of its proper divisors (7004070707411).

21012212122221 is an equidigital number, since it uses as much as digits as its factorization.

21012212122221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7004070707410.

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

Adding to 21012212122221 its reverse (12222121221012), we get a palindrome (33234333343233).

The spelling of 21012212122221 in words is "twenty-one trillion, twelve billion, two hundred twelve million, one hundred twenty-two thousand, two hundred twenty-one".