165665777 has 4 divisors (see below), whose sum is σ = 171378420. Its totient is φ = 159953136.

The previous prime is 165665749. The next prime is 165665779. The reversal of 165665777 is 777566561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 777566561 = 163 ⋅4770347.

It can be written as a sum of positive squares in 2 ways, for example, as 87590881 + 78074896 = 9359^2 + 8836^2 .

It is a cyclic number.

It is not a de Polignac number, because 165665777 - 2¹⁰ = 165664753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165665779) 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, 2856278 + ... + 2856335.

It is an arithmetic number, because the mean of its divisors is an integer number (42844605).

Almost surely, 2^165665777 is an apocalyptic number.

It is an amenable number.

165665777 is a deficient number, since it is larger than the sum of its proper divisors (5712643).

165665777 is an equidigital number, since it uses as much as digits as its factorization.

165665777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5712642.

The product of its digits is 1852200, while the sum is 50.

The square root of 165665777 is about 12871.1218236796. The cubic root of 165665777 is about 549.2173739377.

The spelling of 165665777 in words is "one hundred sixty-five million, six hundred sixty-five thousand, seven hundred seventy-seven".