21011221111081 has 2 divisors, whose sum is σ = 21011221111082. Its totient is φ = 21011221111080.

The previous prime is 21011221111037. The next prime is 21011221111093. The reversal of 21011221111081 is 18011112211012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17327105557056 + 3684115554025 = 4162584^2 + 1919405^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011221111081 - 2⁷ = 21011221110953 is a prime.

It is a super-3 number, since 3×21011221111081³ (a number of 41 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (21011221112081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505610555540 + 10505610555541.

It is an arithmetic number, because the mean of its divisors is an integer number (10505610555541).

Almost surely, 2^{21011221111081} is an apocalyptic number.

It is an amenable number.

21011221111081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011221111081 is an equidigital number, since it uses as much as digits as its factorization.

21011221111081 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 22.

Adding to 21011221111081 its reverse (18011112211012), we get a palindrome (39022333322093).

The spelling of 21011221111081 in words is "twenty-one trillion, eleven billion, two hundred twenty-one million, one hundred eleven thousand, eighty-one".