161317808261 has 2 divisors, whose sum is σ = 161317808262. Its totient is φ = 161317808260.

The previous prime is 161317808237. The next prime is 161317808329. The reversal of 161317808261 is 162808713161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 159688152100 + 1629656161 = 399610^2 + 40369^2 .

It is a cyclic number.

It is not a de Polignac number, because 161317808261 - 2²² = 161313613957 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161397808261) 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, 80658904130 + 80658904131.

It is an arithmetic number, because the mean of its divisors is an integer number (80658904131).

Almost surely, 2^161317808261 is an apocalyptic number.

It is an amenable number.

161317808261 is a deficient number, since it is larger than the sum of its proper divisors (1).

161317808261 is an equidigital number, since it uses as much as digits as its factorization.

161317808261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96768, while the sum is 44.

The spelling of 161317808261 in words is "one hundred sixty-one billion, three hundred seventeen million, eight hundred eight thousand, two hundred sixty-one".