21221101081 has 2 divisors, whose sum is σ = 21221101082. Its totient is φ = 21221101080.

The previous prime is 21221101063. The next prime is 21221101169. The reversal of 21221101081 is 18010112212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12587718025 + 8633383056 = 112195^2 + 92916^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221101081 - 2⁹ = 21221100569 is a prime.

It is a super-2 number, since 2×21221101081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21224101081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610550540 + 10610550541.

It is an arithmetic number, because the mean of its divisors is an integer number (10610550541).

Almost surely, 2^21221101081 is an apocalyptic number.

It is an amenable number.

21221101081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221101081 is an equidigital number, since it uses as much as digits as its factorization.

21221101081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64, while the sum is 19.

Adding to 21221101081 its reverse (18010112212), we get a palindrome (39231213293).

The spelling of 21221101081 in words is "twenty-one billion, two hundred twenty-one million, one hundred one thousand, eighty-one".