261220520161 has 2 divisors, whose sum is σ = 261220520162. Its totient is φ = 261220520160.

The previous prime is 261220520117. The next prime is 261220520173. The reversal of 261220520161 is 161025022162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 261218099025 + 2421136 = 511095^2 + 1556^2 .

It is a cyclic number.

It is not a de Polignac number, because 261220520161 - 2⁹ = 261220519649 is a prime.

It is not a weakly prime, because it can be changed into another prime (261220520101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130610260080 + 130610260081.

It is an arithmetic number, because the mean of its divisors is an integer number (130610260081).

Almost surely, 2^261220520161 is an apocalyptic number.

It is an amenable number.

261220520161 is a deficient number, since it is larger than the sum of its proper divisors (1).

261220520161 is an equidigital number, since it uses as much as digits as its factorization.

261220520161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 28.

The spelling of 261220520161 in words is "two hundred sixty-one billion, two hundred twenty million, five hundred twenty thousand, one hundred sixty-one".