165969561 has 4 divisors (see below), whose sum is σ = 221292752. Its totient is φ = 110646372.

The previous prime is 165969509. The next prime is 165969577.

165969561 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 165969561 - 2¹⁷ = 165838489 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 165969561.

It is not an unprimeable number, because it can be changed into a prime (165965561) 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, 27661591 + ... + 27661596.

It is an arithmetic number, because the mean of its divisors is an integer number (55323188).

Almost surely, 2^165969561 is an apocalyptic number.

It is an amenable number.

165969561 is a deficient number, since it is larger than the sum of its proper divisors (55323191).

165969561 is an equidigital number, since it uses as much as digits as its factorization.

165969561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55323190.

The product of its digits is 437400, while the sum is 48.

The square root of 165969561 is about 12882.9174102763. The cubic root of 165969561 is about 549.5528718628.

The spelling of 165969561 in words is "one hundred sixty-five million, nine hundred sixty-nine thousand, five hundred sixty-one".