21012222221 has 2 divisors, whose sum is σ = 21012222222. Its totient is φ = 21012222220.

The previous prime is 21012222193. The next prime is 21012222239. The reversal of 21012222221 is 12222221012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11275466596 + 9736755625 = 106186^2 + 98675^2 .

It is a cyclic number.

It is not a de Polignac number, because 21012222221 - 2⁶ = 21012222157 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21012222221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21012222821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506111110 + 10506111111.

It is an arithmetic number, because the mean of its divisors is an integer number (10506111111).

Almost surely, 2^21012222221 is an apocalyptic number.

It is an amenable number.

21012222221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012222221 is an equidigital number, since it uses as much as digits as its factorization.

21012222221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21012222221 its reverse (12222221012), we get a palindrome (33234443233).

The spelling of 21012222221 in words is "twenty-one billion, twelve million, two hundred twenty-two thousand, two hundred twenty-one".