206518525815661 has 2 divisors, whose sum is σ = 206518525815662. Its totient is φ = 206518525815660.

The previous prime is 206518525815599. The next prime is 206518525815677. The reversal of 206518525815661 is 166518525815602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 150261775613161 + 56256750202500 = 12258131^2 + 7500450^2 .

It is a cyclic number.

It is not a de Polignac number, because 206518525815661 - 2¹³ = 206518525807469 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 206518525815661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206518525816661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103259262907830 + 103259262907831.

It is an arithmetic number, because the mean of its divisors is an integer number (103259262907831).

Almost surely, 2^{206518525815661} is an apocalyptic number.

It is an amenable number.

206518525815661 is a deficient number, since it is larger than the sum of its proper divisors (1).

206518525815661 is an equidigital number, since it uses as much as digits as its factorization.

206518525815661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 34560000, while the sum is 61.

The spelling of 206518525815661 in words is "two hundred six trillion, five hundred eighteen billion, five hundred twenty-five million, eight hundred fifteen thousand, six hundred sixty-one".