21212286666581 has 2 divisors, whose sum is σ = 21212286666582. Its totient is φ = 21212286666580.

The previous prime is 21212286666499. The next prime is 21212286666587. The reversal of 21212286666581 is 18566668221212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11872331640625 + 9339955025956 = 3445625^2 + 3056134^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212286666581 - 2³⁸ = 20937408759637 is a prime.

It is a super-2 number, since 2×21212286666581² (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 (21212286666587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606143333290 + 10606143333291.

It is an arithmetic number, because the mean of its divisors is an integer number (10606143333291).

Almost surely, 2^{21212286666581} is an apocalyptic number.

It is an amenable number.

21212286666581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212286666581 is an equidigital number, since it uses as much as digits as its factorization.

21212286666581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6635520, while the sum is 56.

The spelling of 21212286666581 in words is "twenty-one trillion, two hundred twelve billion, two hundred eighty-six million, six hundred sixty-six thousand, five hundred eighty-one".