206711216581 has 2 divisors, whose sum is σ = 206711216582. Its totient is φ = 206711216580.

The previous prime is 206711216563. The next prime is 206711216587. The reversal of 206711216581 is 185612117602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 137610579681 + 69100636900 = 370959^2 + 262870^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-206711216581 is a prime.

It is a super-2 number, since 2×206711216581² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206711216587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103355608290 + 103355608291.

It is an arithmetic number, because the mean of its divisors is an integer number (103355608291).

Almost surely, 2^206711216581 is an apocalyptic number.

It is an amenable number.

206711216581 is a deficient number, since it is larger than the sum of its proper divisors (1).

206711216581 is an equidigital number, since it uses as much as digits as its factorization.

206711216581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40320, while the sum is 40.

The spelling of 206711216581 in words is "two hundred six billion, seven hundred eleven million, two hundred sixteen thousand, five hundred eighty-one".