21220111223561 has 2 divisors, whose sum is σ = 21220111223562. Its totient is φ = 21220111223560.

The previous prime is 21220111223537. The next prime is 21220111223573. The reversal of 21220111223561 is 16532211102212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11265045046336 + 9955066177225 = 3356344^2 + 3155165^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220111223561 - 2³⁴ = 21202931354377 is a prime.

It is a super-3 number, since 3×21220111223561³ (a number of 41 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21220111223581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610055611780 + 10610055611781.

It is an arithmetic number, because the mean of its divisors is an integer number (10610055611781).

Almost surely, 2^{21220111223561} is an apocalyptic number.

It is an amenable number.

21220111223561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220111223561 is an equidigital number, since it uses as much as digits as its factorization.

21220111223561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 29.

Adding to 21220111223561 its reverse (16532211102212), we get a palindrome (37752322325773).

The spelling of 21220111223561 in words is "twenty-one trillion, two hundred twenty billion, one hundred eleven million, two hundred twenty-three thousand, five hundred sixty-one".