165561761 has 4 divisors (see below), whose sum is σ = 166036500. Its totient is φ = 165087024.

The previous prime is 165561749. The next prime is 165561779. The reversal of 165561761 is 167165561.

165561761 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 167165561 = 109 ⋅1533629.

It can be written as a sum of positive squares in 2 ways, for example, as 58232161 + 107329600 = 7631^2 + 10360^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-165561761 is a prime.

It is a super-2 number, since 2×165561761² = 54821393410842242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165561661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 236846 + ... + 237543.

It is an arithmetic number, because the mean of its divisors is an integer number (41509125).

Almost surely, 2^165561761 is an apocalyptic number.

It is an amenable number.

165561761 is a deficient number, since it is larger than the sum of its proper divisors (474739).

165561761 is an equidigital number, since it uses as much as digits as its factorization.

165561761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 474738.

The product of its digits is 37800, while the sum is 38.

The square root of 165561761 is about 12867.0805157969. The cubic root of 165561761 is about 549.1024047999.

The spelling of 165561761 in words is "one hundred sixty-five million, five hundred sixty-one thousand, seven hundred sixty-one".