165787561 has 8 divisors (see below), whose sum is σ = 167718600. Its totient is φ = 163862400.

The previous prime is 165787543. The next prime is 165787571.

165787561 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in 4 ways, for example, as 149303961 + 16483600 = 12219^2 + 4060^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 165787561 - 2¹⁷ = 165656489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165787511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 80695 + ... + 82723.

It is an arithmetic number, because the mean of its divisors is an integer number (20964825).

Almost surely, 2^165787561 is an apocalyptic number.

It is an amenable number.

165787561 is a deficient number, since it is larger than the sum of its proper divisors (1931039).

165787561 is a wasteful number, since it uses less digits than its factorization.

165787561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2939.

The product of its digits is 352800, while the sum is 46.

The square root of 165787561 is about 12875.8518553143. The cubic root of 165787561 is about 549.3519209494.

The spelling of 165787561 in words is "one hundred sixty-five million, seven hundred eighty-seven thousand, five hundred sixty-one".