21112122221 has 2 divisors, whose sum is σ = 21112122222. Its totient is φ = 21112122220.

The previous prime is 21112122203. The next prime is 21112122233. The reversal of 21112122221 is 12222121112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20452146121 + 659976100 = 143011^2 + 25690^2 .

It is a cyclic number.

It is not a de Polignac number, because 21112122221 - 2¹⁴ = 21112105837 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21112122221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21112122281) 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 as a sum of consecutive naturals, namely, 10556061110 + 10556061111.

It is an arithmetic number, because the mean of its divisors is an integer number (10556061111).

Almost surely, 2^21112122221 is an apocalyptic number.

It is an amenable number.

21112122221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21112122221 is an equidigital number, since it uses as much as digits as its factorization.

21112122221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64, while the sum is 17.

Adding to 21112122221 its reverse (12222121112), we get a palindrome (33334243333).

The spelling of 21112122221 in words is "twenty-one billion, one hundred twelve million, one hundred twenty-two thousand, two hundred twenty-one".