21011100221 has 2 divisors, whose sum is σ = 21011100222. Its totient is φ = 21011100220.

The previous prime is 21011100217. The next prime is 21011100233. The reversal of 21011100221 is 12200111012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20971094596 + 40005625 = 144814^2 + 6325^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011100221 - 2² = 21011100217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011100211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505550110 + 10505550111.

It is an arithmetic number, because the mean of its divisors is an integer number (10505550111).

Almost surely, 2^21011100221 is an apocalyptic number.

It is an amenable number.

21011100221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011100221 is an equidigital number, since it uses as much as digits as its factorization.

21011100221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21011100221 its reverse (12200111012), we get a palindrome (33211211233).

The spelling of 21011100221 in words is "twenty-one billion, eleven million, one hundred thousand, two hundred twenty-one".