21220111223581 has 2 divisors, whose sum is σ = 21220111223582. Its totient is φ = 21220111223580.

The previous prime is 21220111223573. The next prime is 21220111223593. The reversal of 21220111223581 is 18532211102212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20024139327556 + 1195971896025 = 4474834^2 + 1093605^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220111223581 - 2³ = 21220111223573 is a prime.

It is a super-2 number, since 2×21220111223581² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21220111223561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610055611790 + 10610055611791.

It is an arithmetic number, because the mean of its divisors is an integer number (10610055611791).

Almost surely, 2^{21220111223581} is an apocalyptic number.

It is an amenable number.

21220111223581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220111223581 is an equidigital number, since it uses as much as digits as its factorization.

21220111223581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3840, while the sum is 31.

Adding to 21220111223581 its reverse (18532211102212), we get a palindrome (39752322325793).

The spelling of 21220111223581 in words is "twenty-one trillion, two hundred twenty billion, one hundred eleven million, two hundred twenty-three thousand, five hundred eighty-one".