261656345503661 has 2 divisors, whose sum is σ = 261656345503662. Its totient is φ = 261656345503660.

The previous prime is 261656345503613. The next prime is 261656345503691. The reversal of 261656345503661 is 166305543656162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 247111923402436 + 14544422101225 = 15719794^2 + 3813715^2 .

It is a cyclic number.

It is not a de Polignac number, because 261656345503661 - 2³⁴ = 261639165634477 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261656345503661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261656345503691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130828172751830 + 130828172751831.

It is an arithmetic number, because the mean of its divisors is an integer number (130828172751831).

Almost surely, 2^{261656345503661} is an apocalyptic number.

It is an amenable number.

261656345503661 is a deficient number, since it is larger than the sum of its proper divisors (1).

261656345503661 is an equidigital number, since it uses as much as digits as its factorization.

261656345503661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69984000, while the sum is 59.

The spelling of 261656345503661 in words is "two hundred sixty-one trillion, six hundred fifty-six billion, three hundred forty-five million, five hundred three thousand, six hundred sixty-one".