165505561 has 32 divisors (see below), whose sum is σ = 196156800. Its totient is φ = 138309120.

The previous prime is 165505547. The next prime is 165505573.

165505561 = T₂₃₅ + T₂₃₆ + ... + T₁₀₀₁.

165505561 is nontrivially palindromic in base 10.

It is a cyclic number.

It is not a de Polignac number, because 165505561 - 2⁷ = 165505433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165505661) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 597355 + ... + 597631.

It is an arithmetic number, because the mean of its divisors is an integer number (6129900).

Almost surely, 2^165505561 is an apocalyptic number.

It is an amenable number.

165505561 is a deficient number, since it is larger than the sum of its proper divisors (30651239).

165505561 is a wasteful number, since it uses less digits than its factorization.

165505561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 409.

The product of its (nonzero) digits is 22500, while the sum is 34.

The square root of 165505561 is about 12864.8964628558. The cubic root of 165505561 is about 549.0402667647.

The spelling of 165505561 in words is "one hundred sixty-five million, five hundred five thousand, five hundred sixty-one".