165543661 has 4 divisors (see below), whose sum is σ = 170017852. Its totient is φ = 161069472.

The previous prime is 165543643. The next prime is 165543731. The reversal of 165543661 is 166345561.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 137124100 + 28419561 = 11710^2 + 5331^2 .

It is a cyclic number.

It is not a de Polignac number, because 165543661 - 2⁹ = 165543149 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 4474153 = 165543661 / (1 + 6 + 5 + 5 + 4 + 3 + 6 + 6 + 1).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 165543661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165543461) 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, 2237040 + ... + 2237113.

It is an arithmetic number, because the mean of its divisors is an integer number (42504463).

Almost surely, 2^165543661 is an apocalyptic number.

It is an amenable number.

165543661 is a deficient number, since it is larger than the sum of its proper divisors (4474191).

165543661 is an equidigital number, since it uses as much as digits as its factorization.

165543661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4474190.

The product of its digits is 64800, while the sum is 37.

The square root of 165543661 is about 12866.3771513196. The cubic root of 165543661 is about 549.0823939075.

The spelling of 165543661 in words is "one hundred sixty-five million, five hundred forty-three thousand, six hundred sixty-one".