165221643 has 4 divisors (see below), whose sum is σ = 220295528. Its totient is φ = 110147760.

The previous prime is 165221603. The next prime is 165221669. The reversal of 165221643 is 346122561.

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

It is not a de Polignac number, because 165221643 - 2⁸ = 165221387 is a prime.

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 165221643.

It is not an unprimeable number, because it can be changed into a prime (165221603) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27536938 + ... + 27536943.

It is an arithmetic number, because the mean of its divisors is an integer number (55073882).

Almost surely, 2^165221643 is an apocalyptic number.

165221643 is a deficient number, since it is larger than the sum of its proper divisors (55073885).

165221643 is an equidigital number, since it uses as much as digits as its factorization.

165221643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55073884.

The product of its digits is 8640, while the sum is 30.

The square root of 165221643 is about 12853.8571253924. The cubic root of 165221643 is about 548.7261350518.

The spelling of 165221643 in words is "one hundred sixty-five million, two hundred twenty-one thousand, six hundred forty-three".