161641561 has 2 divisors, whose sum is σ = 161641562. Its totient is φ = 161641560.

The previous prime is 161641549. The next prime is 161641591. The reversal of 161641561 is 165146161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 86490000 + 75151561 = 9300^2 + 8669^2 .

It is a cyclic number.

It is not a de Polignac number, because 161641561 - 2¹³ = 161633369 is a prime.

It is a super-2 number, since 2×161641561² = 52255988485033442, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (161641591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80820780 + 80820781.

It is an arithmetic number, because the mean of its divisors is an integer number (80820781).

Almost surely, 2^161641561 is an apocalyptic number.

It is an amenable number.

161641561 is a deficient number, since it is larger than the sum of its proper divisors (1).

161641561 is an equidigital number, since it uses as much as digits as its factorization.

161641561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 31.

The square root of 161641561 is about 12713.8334502226. The cubic root of 161641561 is about 544.7338273238.

The spelling of 161641561 in words is "one hundred sixty-one million, six hundred forty-one thousand, five hundred sixty-one".