261564211021777 has 2 divisors, whose sum is σ = 261564211021778. Its totient is φ = 261564211021776.

The previous prime is 261564211021769. The next prime is 261564211021787. The reversal of 261564211021777 is 777120112465162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 214992307963456 + 46571903058321 = 14662616^2 + 6824361^2 .

It is a cyclic number.

It is not a de Polignac number, because 261564211021777 - 2³ = 261564211021769 is a prime.

It is not a weakly prime, because it can be changed into another prime (261564211021787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130782105510888 + 130782105510889.

It is an arithmetic number, because the mean of its divisors is an integer number (130782105510889).

Almost surely, 2^{261564211021777} is an apocalyptic number.

It is an amenable number.

261564211021777 is a deficient number, since it is larger than the sum of its proper divisors (1).

261564211021777 is an equidigital number, since it uses as much as digits as its factorization.

261564211021777 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1975680, while the sum is 52.

The spelling of 261564211021777 in words is "two hundred sixty-one trillion, five hundred sixty-four billion, two hundred eleven million, twenty-one thousand, seven hundred seventy-seven".