161345691721 has 2 divisors, whose sum is σ = 161345691722. Its totient is φ = 161345691720.

The previous prime is 161345691713. The next prime is 161345691733. The reversal of 161345691721 is 127196543161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 97882005321 + 63463686400 = 312861^2 + 251920^2 .

It is a cyclic number.

It is not a de Polignac number, because 161345691721 - 2³ = 161345691713 is a prime.

It is not a weakly prime, because it can be changed into another prime (161345691421) 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, 80672845860 + 80672845861.

It is an arithmetic number, because the mean of its divisors is an integer number (80672845861).

Almost surely, 2^161345691721 is an apocalyptic number.

It is an amenable number.

161345691721 is a deficient number, since it is larger than the sum of its proper divisors (1).

161345691721 is an equidigital number, since it uses as much as digits as its factorization.

161345691721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 272160, while the sum is 46.

The spelling of 161345691721 in words is "one hundred sixty-one billion, three hundred forty-five million, six hundred ninety-one thousand, seven hundred twenty-one".